Monday, October 28, 2013

CBSE I NCERT Topic_ Interesting Atmospheric Refraction Phenomena (Light)

1. A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard. What advice will a doctor give to her?

Ans: The student is suffering from myopia (near sightedness). Doctor advises her to use a concave lens of appropriate power to correct this defect.

2. How are we able to see nearby and also the distant objects clearly?

Ans: Human eye is able to see nearby and distant objects clearly by changing the focal length of the eye lens using its power of accommodation.

3. A person needs a lens of power –4.5 D for correction of her vision.
(a) What kind of defect in vision is she suffering from?
(b) What is the focal length of the corrective lens?
(c) What is the nature of the corrective lens?

Ans: (a) Negative sign of power of lens indicates that focal length is negative that is only possible in concave lens that is used for correction of Myopia
(b) f =1/-4.5 =-2/9= – 0.22 m,
(c) The nature of the corrective lens is diverging rays of light.

4. Is the position of a star as seen by us its true position? Justify your answer.
Ans: No. light from stars undergoes atmospheric refraction which occurs due to the variation in air density.

5. Why do we see a rainbow in the sky only after rainfall?
Ans: We see a rainbow in the sky only after rainfall because the water droplets behave like prisms and disperse sunlight. due to atmospheric refraction and total internal refraction. A rainbow is always formed in a direction opposite to that of the sun. The water droplets act like small prisms. They refract and disperse the incident sunlight, then refract it internally and finally refract it again when it comes out of the raindrop.

6. Why is the colour of the clear sky blue?

Ans: Blue coloour gets scattered the maximum due to less wave velocity.

7. What is the difference in colours of the Sun observed during sunrise/sunset and noon? Give explanation for each.

Ans: During sunrise and sunset the sun appears reddish whereas at noon the sun appears white.
At sunrise and sunset the light coming from the sun has to travel a longer distance through the atmosphere to reach us. Ttherefore the blue and green components of white light are gets scattered away (removed) almost completely leaving the longer wavelength. Hence, during sunrise and sunset the sun appears reddish.
When the sun is overhead at noon, then the light coming from the sun has to travel a relatively shorter distance through the atmosphere to reach us. As a result, only a little of the blue colour of the white light is scattered (most of the blue light remains in it). Since the light coming from the overhead sun has almost all its components colours in the right proportion, therefore, the sun appears white

8. Chicken can see only in bright light. What type of cells is present in its retina?

Ans: Its retina has only rod cells and no cone cells.

9. Give reason: What will be colour of the sky in the absence of atmosphere?

Ans: In the absence of any atmosphere, there will be no scattering of sunlight and the sky will appear dark.

10. Give reason: Why are the traffic light signals (or danger signals) of red colour?

Ans: In the visible spectrum, the red color has the largest wavelength. The red colour is least scattered by fog or dust particles. Therefore, we can observe red color easily even in foggy and dusty conditions.
11. Why does the sky appear dark and black to an astronaut instead of blue?

Ans: This is because there is no atmosphere containing air in the outer space to scatter light. Since there is no scattered light, which can reach our eyes in outer space, therefore, the sky looks dark and black there. This is why the astronauts who go to outer space find the sky to be dark and black instead of blue.

12. What is Tyndall Effect? Explain with an example.

Ans. The scattering of light by particles in its path is called Tyndall Effect.
When a beam of sunlight enters a dusty room through a window then its path becomes visible to us. This is because the tiny dust particles present in the air of room scatter the beam of light all around the room. And when thus scattered light enters our eyes, we can see the beam of light. Thus, an example of Tyndall effect is the way a beam of sunlight becomes visible as it passes through dust particles in the air of a room.

13. The sun near the horizon appears flattened at the sun set and sun rise. Explain why.

Ans: - This is due to atmospheric refraction. The density and refractive index of the atmosphere decreases with altitude, so the rays from the top and bottom portion of the sun on horizon are refracted by different degrees. This causes the apparent flattening of the sun. But the rays from the sides of the sun on a horizontal plane are generally refracted by the same amount, so the sun still appears circular along the sides.  

14.Why We can see the sun about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset 

Ans: We can see the sun about 2 minutes before the actual sunrise, and about 2 minutes after the actual sunset because of atmospheric refraction. By actual sunrise, we mean the actual crossing of the horizon by the Sun.

When the sun just below the horizon its rays enters earths atmosphere and refracted towards the earth. Refracted ray that reach us making it appears the sun reaches to horizon. This is the apparent sunrise. But actual sunrise occur when sun reach to horizon. Conversely apparent sunset occur slightly latter than actual sun set . Since light from sun already below the horizon it refract through atmosphere enabling us to see apparent sun set even sun has already set.

15.What is night blindness? How is it caused and can it be corrected ?

Ans. Some persons have difficulty in seeing the objects in dim light during night. This defect of eye is called night-blindness.
Causes are :
(1) Lack of vitamin A in the food.
(2) Improper functioning of rod-shaped cells.
It is corrected by using contact lenses. Soft contact lenses allow more of oxygen to reach than hard lenses. They bend the rays of light to correct their refractive angle, which enables a sharp image to be formed at the retina. 


SECTION - A   (Reading – 20 Marks)   

1. Read the poem given below and complete the sentences that follow. 
 Just for a handful of silver he left us, 
 Just for a riband to stick in his coat- 
 Found the one gift of which fortune bereft us, 
 Lost all the others she lets us devote; 
 They, with the gold to give, doled him out silver, 
 So much was theirs who so little allowed; 
 How all our copper had gone for his service! 
 Rays- were they purple, his heart had been proud, 
 We that had loved him so, followed him, honoured him, 
 Lived in his mild and magnificent eye, 
 Learned his great language, caught his clear accents, 
 Made him our pattern to live and to die 
 He alone breaks from the van and the freemen, 
 He alone sinks to the rear and the slaves !  
                                                      Robert Browning 

 (A) The person who left them is their ___________ . 
 (B) He left them for the sake of __________ . 
 (C) The speaker and his comrades were __________ people in their country. 
 (D) Now the speaker and his comrades __________ him. 
 (E) Find out a word from the passage that means opposite to the word ‘front’ 

2. Read the following passage carefully :-  

 Our opportunities are great but let me warn you that when power outstrips ability, we will fall on evil days. We should develop competence and ability which would help us utilise the opportunities which are now open to us. From tomorrow morning from midnight today-we cannot throw the blame on the Britishers. We have to assume the responsibility ourselves for what we do. A free India will be judged by the way in which it will serve the  interests of the common man in the matter of food, clothing, shelters and social activities.Unless we destroy corruption in high places and root out every trace of nepotism, love of power , profiteering and black marketing which have spoiled the good name of this country in recent times, we will not be able to raise the standards of efficiency in administration as in  well as the production and distribution of the necessary goods of life. 

Complete the following statements by choosing the most appropriate options from those given below. 

(a) We fall on evil days when power becomes more important than : 

 (i) wisdom (ii) wealth (iii) fame (iv) ability 
(b) The two things that help us to utilise the opportunities are our : 

 (i) competence and power (ii) power and ability  (iii) competence and ability (iv) power and wealth 

(c) The common man should be provided with : 
 (i) food (ii) clothing  (iii) shelter (iv) food clothing shelter and social activities 

(d) The good name of our country has been spoiled because of : 

 (i) corruption 
 (ii) nepotism 
 (iii) love of power, profiteering and black marketing 
 (iv) all of the above. 

 (e) The word ‘assume’ means: 
 (i) think (ii) guess (iii) take on (iv) understand 

3. Read the passage given below and complete the statements that follow : 
 Vegetable oil has been known since antiquity. No household can get on without it, for it is used in cooking. Perfumes may be made from the oils of certain flowers. Soaps are  made from vegetables and animal oils. 
To the ordinary men, one kind of oil may be as important as another. But when the politician  or the engineer refers to oil he almost always means mineral oil, the oil that drives tanks, aeroplanes and warships, motor cars and diesel locomotives, the oil that is used to lubricate all kinds of machinery. When it is refined into petrol it is used to drive the internal  combustion engine. To it we owe the existence of the motor car, which has replaced the private carriage drawn by the horse. To it we owe the possibility of flying. It has changed the method of warfare on land and at sea. This kind of oil comes out of the earth. Because it burns well, it is used as a fuel and in some ways it is superior to coal in this respect. Because it burns brightly it is used for illumination. Because it is very slippery, it is used for lubrication. Two metal surfaces rubbing together cause friction and heat. But if they are separated by a thin film of oil the friction and heat are reduced.  No machine would work for long if it were not properly lubricated. 

(a) The most important use of vegetable oil is its __________ . 
(b) Mineral oil is different from vegetable oil as it __________ . 
(c) Mineral oil has changed everything. The most important change is that it 
 drives __________ . 
(d) __________ reduces the frictions and heat in machines etc. 
(e) The ‘word’ illumination means __________ . 

4. Read the passage given below and complete the sentences that follow by choosing the appropriate answers from the given options. 1x5=5 
 As the tortoise tucks its feet and head inside the shell and will not come out even though you may break the shell into pieces, even so the character of the man who has controls over his motives and organs, is unchangeably established. He controls his own inner forces, and nothing can draw them out against his will. By this continuous force of good thoughts and good impressions moving over the surface of the mind, the tendency to do good, becomes strong, and in consequence we are able to control the ‘Indriyas’ (sense-organs, the nerve centers). In this way alone is character formed, and only a man of character can get at the truth. Such a man is safe for ever; he cannot do any evil. You may place him in any company, but there will be no danger for him. There is a still higher state than having this good tendency, and that is the desire for liberation. Liberation means full freedom-freedom from the bondage of evil. A golden chain is as much a chain as an iron one. There is a thorn in my finger, and I use another to take the first one out; and when I have taken it out, I throw both of them aside. I have no necessity for keeping the second thorn, because 
it is a thorn after all. So bad tendencies are to be counteracted by good ones, and bad impressions on the mind should be removed by the fresh waves of good ones, until all that is evil almost disappears, or is subdued and held in control in a corner of the mind; but after that the good tendencies also have to be removed. Thus the attached becomes, unattached. 

(a) The comparison between the tortoise and the man reveals that : 
 (i) Man is superior to tortoise.                                     
(ii) Tortoise is on a par with man. 
 (iii) Man who has control over his motives and organs is  weak. 
 (iv) Man who has control over his motives and organs is firm. 

 (b) The control of ‘Indriyas’ leads to : 
 (i) meditation 
 (ii) strength 
 (iii) character formation 
 (iv) renunciation of the world 

(c) Liberation is : 
 (i) freedom of the body 
 (ii) freedom from bondage of passions 
 (iii) freedom from bondage of worldly things 
 (iv) freedom from bondage of evil 

(d) Attached becomes unattached when : 
 (i) evil is removed 
 (ii) worldly desires are fulfilled 
 (iii) even good tendencies disappear 
 (iv) God blesses 

(e) The word ‘subdued’ means : 
 (i) passive (ii) inactive 
 (iii) suppressed (iv) inactivated 

 SECTION - B         (Writing – 25 Marks) 

5. Your grandmother completed 80 years of her age on January 15, 2012. Celebrating her 80th  birthday was an event for the family. Describe the event giving all the relevant details in  about 80 words. 

6. While reading a newspaper, you come across the following news item 
                       ‘Ready for the Olympics’ 12 ?  Is India listening ? 
=> Eighteen months before competition gets underway, nearly 75 percent of construction is now complete, with main venues due to be finished next year. 
=>  Inside the showpiece stadium in Stratford, east London, seats are already installed in some parts while the outline of the track and field can be seen.  
=> Elsewhere the curved roofs of the aquatics centre stand out on the skyline with only some work to be completed. 

Based on the information given above write an e-mail to your friend expressing your views in the light of what happened at the CWG, New Delhi (120 words) 
Date : ___________________________________________________ 
From : ___________________________________________________ 
Subject : _________________________________________________ 
To : _____________________________________________________ 

7. Wildlife tourism earns a lot of revenue for the country but is also a threat for the delicate  wildlife. Write a speech in about 150 words to be presented in the school assembly. Use ideas from the unit, ‘Travel and Tourism’, the visual and your own ideas. Imagine you are Shweta/ Sameer, Cultural President of your school.

SECTION - C (Grammar – 20 Marks)

8.Choose the most appropriate options from the ones given below to complete the following passage. Write the answer in your answer sheet against the correct blank number. Do not copy the whole passage. Tokyo was rocked by its 
(a)_____________ earthquake in more than a year today, but escaped 
(b)____________________ little damage because it 
(c)_______________ centered far beneath the floor of the Pacific Ocean. The quake 
(d)_________________ struck shortly before noon with a magnitude of 6.6 
(e)___________________ large buildings swayed back and forth. The intense 
(f)________________ for about one minute caught many people 
(g)_______________ guard in Tokyo and the other cities
(h)_____________ east.

(a) (i) big (ii) bigger (iii) biggest (iv) very big

(b) (i) from (ii) by (iii) with (iv) for

(c) (i) is (ii) was (iii) has (iv) have

(d) (i) who (ii) whom (iii) whose (iv) which

(e) (i) make (ii) made (iii) send (iv) sent

(f) (i) shake (ii) shaker (iii) shaking (iv) shook

(g) (i) in (ii) on (iii) of (iv) off

(h) (i) to (ii) toward (iii) for (iv) forward

9.Look at the notes given below and complete the paragraph with the most appropriate options. Write the answers in your answer sheet against the correct blank numbers :

Students – British university – refuse – kill insects – future ecologists – respect –nature – only – categorise them – no collecting or killing – students suggestion –emphasis – observe, identify, study – natural habitats

Students at a British university (a) _________on moral grounds. They argue that the university should encourage future ecologists (b) _________ . The students maintain that they should only have to categorise insects (c) _________ .They (d) _________ the university should place more emphasis on observing, identifying and studying living creatures within their natural habitats.

(a) (i) were scared (ii) were anxious (iii) refused to kill insects (iv) were scared to kill insects 
(b) (i) to love nature (ii) to conserve nature (iii) to serve nature (iv) to respect nature 
(c) (i) preserve them (ii) kill the insects (iii) observe them (iv) and not collect and kill them 
(d) (i) argued that (ii) emphasized that (iii) suggest that (iv) they insist that

10 Re-arrange the following words/phrases to form meaningful sentences. The first one has been done as an example.
 E.g. The watermelon/thirst quenchers/in summers/is/one of the best

One of the best thirst quenchers in summers is the watermelon (a) around/it is /96 countries/ cultivated in/the world (b) in Africa / about 5000 years / grown /ago/ it was / first (c) say that / at the / it was grown/ some researchers/ same time/ in India (d) the travellers/ across a desert/ it was/ when they/ used by/ travelled

11.In the following passage there is an error in each line. Write the incorrect word and the correction in the space provided.
                                                                                      Error   Correction
In the absence of rain all the river                            (a) ________ ________ 
get dry. Crops failed in the absence of                    (b) ________ ________ 
water. Their is a food shortage and we                   (c) ________ ________ 
have to go with other countries with a                    (d) ________ ________ 
begging bowl. Who don’t know the                       (e) ________ ________
advantages of a trees? In the absence of                (f) ________ ________ 
forests we get not fruits, nuts, fibers                      (g) ________ ________ 
and herbs at medicinal use.                                   (h) ________ ________

12.Complete the news reports accompanying the following headlines.
 (a) Two killed in Blue Line Accidents __________ buses here on Monday, one, an 18 year old girl and the other, a cyclist.
(b) Assam seeks CBI probe The Assam government today _______________ into the violence during the anti reservation rally last week. 
(c) Two die of burns Two senior executives of Baranagar Jute Factory ___________ in the factory premises. 
(d) Cold wave grips Delhi Delhi ________________ by intense cold wave as the temperature plummeted 5 degrees below the normal to settle at 0.3 deg. C

SECTION - D (Literature – 25 Marks)

13. A) Read the extract given below and answer the questions/complete the statements that follow by choosing the most appropriate options:

I met a traveller from an antique land Who said : Two vast and trunkless legs of stone Stand in the desert. Near them, on the sand ,

(a) ‘I’ here refers to :     
(i) the poet
(ii) the sculptor
(iii) the traveler
(iv) Ozymandias

(b) What happened to the statue ?

 (i) It became trunkless.
(ii) Its face disappeared.
(iii) Its face was dismantled .
(iii) It had two vast legs

(c) The poem is set in : 
(i) a palace
(ii) an ancient land 
(iii) a wilderness
 (iv) none of the above

14 Answer any four of the following questions in 30-40 words each :

(a) Why couldn’t John Hallock give his whole time to writing?
(b) How did Patol Babu completely get over his apathy?
 (c) What was the terrible deed done by the old Mariner ? Why was it terrible?
(d) Who was Sebastian Shultz ? How did he meet with an accident ?
 (e) What is your impression about Julius Caesar’s character.

15.Answer the following in about 120 words. ‘Everything that I’ve described is true virtually’? says the narrator. Even the title of the story is ‘Virtually True’. Justify the statement of the narrator and also the title of the story. 
What does Antony say in his speech? Why is it more effective than that of Brutus ?


CBSE I NCERT 10th Numerical Problem solved For _ Reflection and reflection of light

Q. 1. A concave mirror of focal length 20cm is placed 50 cm from a wall. How far from the wall an object be placed to form its real image on the wall?

Soluion : V=-50 cm    F=-20cm

From mirror formula 1/u = 1/f – 1/v

= -1/20+ 1/50 =-3/100      U = -33.3 cm

Therefore the distance of the object from the wall x = 50 – u 

X = 50 – 33.3 = 16.7 cm.

Q.2. An object is placed at a distance of 40cm from a concave mirror of focal length 15cm. If the object is displaced through a distance of 20 cm towards the mirror, By how much distance is the image displaced?

Answer:  Here f = -15 cm, u = -40 cm

Now 1/f = 1/u + 1/v

Then 1/v = 1/f – 1/u

Or   V= uf/u-f = -40 X -15/25 = -24 cm

Then object is displaced towards the mirror let u1 be the distance object from the

Mirror in its new position.

Then u1 = -(40-20) = -20cm

If the image is formed at a distance u1 from the mirror then

v= u1f/u1-f = -20X-15/-20+15 = -60 cm.  =  - 20 x-15/-20+15 = -60 cm. 

Therefore the image will move away from the concave mirror through a distance equal to 60 – 24 = 36 cm.

Q.3. An object is placed at distance of 25 cm from a spherical mirror and its image is formed behind the mirror at distance of 5 cm. Find focal length? Is it concave or convex mirror? Answer:
Here u = -25 cm , v = 5 cm from the mirror formula 1/f =1/u + 1/v

Then 1/f = -1/25 + 1/5 = 4/ 25

F = 6.25 cm

As the focal length is positive the mirror is convex in nature. 

Q. An object is placed in front of a convex mirror of radius of curvature 40 cm at a distance of 10 cm. Find the position, nature and magnification of mirror.
Here u = -10 cm, R = -40 cm

Then f = R/2 = - 20 cm

From the mirror formula 1/v = 1/f – 1/ u = -1/20 + 1/10 = 1/20.

V= 20 cm so v is positive , a virtual and erect image will be formed on the other side of the object, i.e; behind the mirror.  M=-v/u = -20/-10 = 2 

Q. An object is kept in front of a concave mirror of focal length of 15 cm. the image formed is 3 times the size of the object. Calculate the two possible distances of the object from the mirror. 

Case:1. Image is real. M = -3

Here f= -15 cm

Now m=-v/u = -3

Or , V = 3u

From the mirror formula

1/f = 1/u+1/v

-1/15 = 1/u + 1/3u

U= - 20 cm.

Case:2. When the image is virtual m = 3

Now m = -v/u = 3

Or,    V=-3
From the mirror formula


Then -1/15 = 1/u-1/3u

2/3u = -1/15


Q. Refractive index of glass is 1.5 and that of water is 1.3. if the speed of light in water is 2.25X108m/s. What is the speed of light in glass?
 Here ng=1.5 and nw=1.3 let v1 and v2 be the speeds of light in glass and water respectively. If c is the speed of light in air then

c/v1=1.5 and c/v2=1.3

then v1/v2= 1.3/1.5


v1=1.95X108 m/s

Q. A light of wave length 6000A0 in air enters a medium with refractive index 1.5. what will be the frequency and wave length of light in medium?

Here wave length of light in air l=6000A0 = 6X10-7m

Refractive index of medium = 1.5 = n

The frequency of light does not change, when light travels from air to a refracting medium.

n=c/l = 3X108/6X10-7 = 5X1014Hz

The wave length of light in the medium l1=l/n = 6000/1.5 = 4000A0

Q. Convex lens made up of glass of refractive index 1.5 is dipped in turn in 
(i) Medium A of n=1.65
 ii) Medium B of n = 1.33. 
Explain giving reasons Whether it will behave as a converging lens or diverging lens in each of the


Two cases.
Here ng
Let fair be the focal length of lens in air then
   1/fair = (ng-1)(1/R1-1/R2)
 (1/R1-1/R2) = 1/fair(ng-1) = 2/fair……………………………..(1)

(i)  When lens is dipped in a medium A here nA = 1.65

Focal length be fA when dipped in a medium A then 1/fA=(nA-1)(1/R1-1/R2)

Using equation (1) we have

1/fA = (1.5/1.6 5-1) X 2/fair = -1/5.5 fair

FA = -5.5 fair

As sign of fA is opposite to that of fair, the lens will behave as diverging lense.

(ii)   When lens is dipped in a Medium B nB = 1.33

Let fB be the focal length of lens when dipped in medium B

Then 1/fB = (ng-1)(1/R1-1/R2) =(ng/nB-1) )(1/R1-1/R2)

1/fB =(1.5/1.33-1)X2/fair = 0.34/1.33 fair = F= 3.91

fair as the Sign of fB is same as that of fair the lens will behave as a converging lens

Q. A convergent beam of light passes through a diverging lens of focal length 0.2 meters comes to focus at a distance 0.3 meters behind the lens find the position of the point at which the beam would converge in the absence of lens?

Answer: F=-0.2 m, v=0.3 m

From the lens equation 1/f = 1/v-1/u

1/u = 1/v-1/f = 1/0.3-1/-0.2 = 50/6

U=6/50 = 0.12 m

In the absence of lens the beam would converge at a distance 0.12 m from the present position of the lens.

Q. A beam of light converges to a point P. A lens is placed in the path of convergent beam 12 cm from the point P. At what point the beam converges if the lens is   (a) a concave lens of focal length 16 cm  (b) a convex length of focal length 20 cm.

Answer: (a) here u =12cm f = -16 cm the lens equation we have

V=uf/u+f=12X-16/12-16 = 48 cm 

as v is positive the beam converges on the same side that of point P

b) Here u = 12 cm , f =20 cm from the lens equation we have

V=uf/u+f = 12X20/12+20 = 240/32 = 7.5 cm

As  v is positive the beam converges on the same side as that of point of P

Q.A converging and a diverging of equal focal lengths are placed co-axially in  Contact. Find the focal length and power of the combination.

Answer: Let f and –f are be the focal length of the converging and diverging lens respectively then focal length of the combination

1/F = 1/f – 1/f = 0

Power of the combination p = 1/F = 0.

Practice Questions

1. An object is placed in front of a concave mirror of radius of curvature 15cm at a distance of (a) 10cm. and (b) 5cm. Find the position, nature and magnification of the image in each case.

2. An object is placed 15cm from a concave mirror of radius of curvature 60 cm. Find the position of image and its magnification?

3. An object is kept at a distance of 5cm in front of a convex mirror of focal length 10cm. Give the position, magnification and the nature of the image formed.

4. An object is placed at a distance of 50cmfrom a concave lens of focal length 20cm. Find the nature and position of the image.

5. The power of a lens is 2.5 dioptre. What is the focal length and the type of lens?

6. What is the power of a concave lens of focal length 50cm?

7. Find the power of a concave lens of focal length 2m.

8. Two lens of power +3.5D and -2.5D are placed in contact. find the power and focal length of the lens combination.

9. A convex lens has a focal length of 20 cm. Calculate at what distance from the lens should an object be placed so that it forms an image at a distance of 40cm on the other side of the lens. State the nature of the image formed?

10. A 10cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30cm. The distance of the object from the line is 20cm.find the i)position ii)nature and iii) size of the image formed.

11. Find the focal length of a line power is given as +2.0D.

12. With respect to air the refractive index of ice and rock salt benzene are 1.31 and 1.54 respectively. Calculate the refractive index of rock salt with respect to ice.

13. An object 5cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30cm. Find the position of the image, its nature and size.

14. The far point of a myopic person is 150cm in front of the eye. Calculate the focal length and the power of the lens required to enable him to see distant objects clearly.
Links For   CBSE Class X Science Term-II

Saturday, October 26, 2013

Biology (Science) Guess Paper Summative Assessment – II, 2014 Class – X

1 mark Questions 1 x 5 = 5
1. Questions: In a food chain consisting of snake, insect, grass and frog, assign an appropriate trophic level to frog.
2. Questions: Producers always occupy the first trophic level in any food chain. Why ?

3. Questions: Name the bacteria responsible for nitrification in nature.
4. Questions: Use of paper bags is more environment friendly than the use of polythene bags for packaging. Justify.

5. Questions: Name any two factors responsible for the formation of soil.

2 marks Questions 2 x 10 =20
6. Questions: Name those parts of a flower which serve the same function as the following do in the animal
(i) Testis (ii) Ovary (iii) Eggs (iv) Sperms

7. Questions: What are fossil fuels ? How are they formed ?

8. Questions: What is ozone ? How does it protect the organisms on the Earth ?

9. Questions: What are sexually transmitted diseases ? Name an STD which damages the immune system of human body ?

10. Questions: Pre - natal sex determination has been prohibited by law. State two reasons.

11. Questions: What is placenta ? State its any two roles during pregnancy.

11. Questions: List any four stakeholders which may help in the conservation of forests

12. Questions: (a) Why are coal and petroleum called fossil fuels ? (b) Name any two elements present in fossil fuels in addition to carbon.

13.Questions: How can we as an individual help in reducing the use of fossil fuels ? Mention two ways.
14.Questions: State in brief two functions of copper - T used by some women.
(i) Write one main characteristic feature that differentiates Gymnosperms from Angiosperms.
(ii) Give one example of each of a Gymnosperm and an Angiosperm.3 marks 

(i) Identify the class of animals having the following characteristic features.
a) The warm blooded animals that lay eggs and have four chambered heart and a covering of feathers.
b) The cold blooded animals having scales and they breathe through lungs.
(ii) Give one example of an animal belonging to each of these classes.

17.Questions: Distinguish between analogous organs and homologous organs. Identify the analogous and homologous organs among the following :
Wings of an insect, wings of a bat, forelimbs of frog, forelimbs of human. 1

18.Questions:Explain with the help of flow chart - “What determines the sex of a child genetically”

19. Questions:What is the importance of D.N.A copying in reproduction ? Why is variation beneficial to the species but not necessary for the individual ? Explain.

20.Questions: (a) Are the wings of a butterfly and the wings of a bat analogous organs or homologous organs ? Justify your answer. (b) State the role of father and mother in the determination of sex of new born child. Support your answer with a suitable illustration.

21.Questions: (a) Identify the asexual method of reproduction in each of the following organisms:
(i) rose (ii) yeast (iii) planaria
(b) What is fragmentation ? Name a multhcellular organism which reproduces by this method.

22.Questions: List three groups of plants. Which plants are referred to as vascular plants ? Out of these which group is further classified on the basis of number of cotyledon ? State its two characteristics.

23. Questions: List in the tabular form any three differences between the Aves and the Mammalia group.

24. Questions: 
a) Why taking an antibiotic is not effective in the common cold ?
b) Name two diseases against which infants below one year are vaccinated.
(c) List two symptoms of any one of these diseases.

25.Questions: Draw the labelled diagram of female reproductive system. Name the organ which provides nutrition to embryo? Where is it located?

5 marks

26. Questions:
a) What is the role of seminal vesicles and the prostate gland ? What are the three categories of contraception methods ? Write briefly about each. [2+3]

(a) Draw longitudinal section of a flower and label on it the following : [2+3 ]
(i) Ovary (ii) Style (iii) Stigma (iv) Anther
(b)Why is vegetative propagation practised for growing some plants ? Give two examples of plants grown by this method.

28. Questions:
(a) Differentiate between germination and fertilization. 2+3
(b) State in brief the functions of the following parts of the human male reproductive system :
(i) Scrotum (ii) Testes (iii) Vas deferens

 (a) Differentiate between pollen grain and ovule. 2+3
(b) State in brief the functions of the following parts of the human female reproductive system.
(i) Ovary (ii) Fallopian Tube (iii) Uterus

(a) List two advantages of sexual reproduction over asexual reproduction.5

(b) Name the type of asexual reproduction seen in : (i) Plasmodium (ii) Planaria
(c) Draw a diagram of Rhizopus showing the location of : (i) Sporangium (ii) Rhizoidal hyphae.
(d) How will an organism be benefited if it reproduces through spores ?

Wednesday, October 23, 2013

CBSE Science X Sample Paper 2014[SA_II]

CBSE Science X Question paper of 2011 solution for preparation of 2014
 1. What are the various steps in a food chain called?
Solution: Trophic levels.
2. What is the important function of presence of ozone in earth’s atmosphere?
Solution: The ozone layer prevents the harmful UV rays from entering into the earth’s atmosphere.
3. Write the electron dot structure of ethane molecule, C2H6

4. What makes the earth’s atmosphere a heterogeneous mixture?
Solution: Different gases like  oxygen, nitrogen, argon and CO2 with other gases make the earth’s atmosphere a heterogeneous mixture.
5. List any four characteristics of a good fuel.
Solution: Characteristics of a good fuel are :
i. low ignition temperature.
ii. High calorific value
iii. Environmental friendly.
iv. Easily available and accessible
6. What are non-renewable resources of energy? Give two examples of such resources.
Solution: Non-renewable resources of energy are those energy resources that cannot be replenished in reasonable period. Two examples of non-renewable resources are coal and petroleum.
7. (i) How do you calculate the possible valency of an element from the electronic configuration of its atoms?
(ii) Calculate the valency of element X whose atomic number is 9.
Solution: (i) The electrons present in the last shell determine the valency of a particular element.
Number of valence electrons ≤ 4: valency = number of valence electrons
Number of valence electrons > 4: valency = 8 - number of valence electrons
(ii) The electronic configuration of element X with atomic number 9 is 2,7
Its valency = 8–7 =1
Hence, the valency of element with atomic number 9 is 1.
8. On the basis of electronic configuration, how will you identify the first and the last element of a period?
Solution: If the number of valence electron is 1 then the element is said to be the first element of a period, If the number of valence electrons are 8, the element is said to be the last element of a period.

9. State the two laws of reflection of light.

10. The stars appear higher from horizon than they actually are. Explain why it is so.
Stars appear slightly higher from the horizon due to atmospheric refraction. The atmosphere bends the starlight towards the normal. This apparent positioning is not stationary but keeps changing.
11. Explain why the planets do not twinkle but the stars twinkle.
The planets being closer to the Earth do not appear as point sources of light. The planet covers a small circular area in space, when viewed from Earth. So, even if light from one point in the circular disc is blocked, light from other points reaches our eyes. As the light from the planets are not completely blocked from our sight and they do not twinkle. Stars on the other hand are point sized objects and twinkle by atmospheric refraction of light.
12. Write any two differences between binary fission and multiple fission in a tabular form as observed in cells of organisms.
Solution: Two differences between binary fission and multiple fission are as follows:
Binary Fission
Multiple fission
The single cell divides into halves.                    
The single cell divides into many daughter cells
Binary fission is of two types; along any
plane or longitudinally.
Multiple fission occurs along only one plane.

Amoeba (along any plane), Leishmania (longitudinally)
Example: Plasmodium

13. Why is DNA copying an essential part of the process of reproduction?
Solution: DNA copying mechanism is significant in reproduction because it enables to make copies of the blueprint of the body design of organism of a particular species. This in turn ensures that the basic body design of organisms of a particular species is same and they look similar.
 14. Explain the terms: (i) Speciation (ii) Natural selection
(i) Speciation - Speciation is an evolutionary phenomenon by which new species are formed. There are three models of speciation:
1. When the groups that evolve to be separate species are in different geographic locations and are isolated geographically from each other
2. When the groups that evolve to be separate species are geographic near and the individuals can move one species area to others.
3. When the groups that evolve to be separate species occur together  in the same geographic area.
(ii) Natural selection – Natural selection is a key mechanism in evolution.  It is a process that results in an increased survival and reproductive success of individuals that are well adjusted to the environment. The theory of natural selection was given by Charles Darwin.
15. Explain how equal genetic contribution of male and female parents is ensured in the progeny.
The genetic material of a cell is stored in the DNA. During sexual reproduction, the genetic material from both the parents is transferred to the offspring. All human beings have 23 pairs of chromosomes out of which two
chromosomes are sex chromosomes. These sex chromosomes are responsible for determining the sex of a child.
(i) The sex chromosomes are represented by X and Y. Females have two X chromosomes (XX) and males have one X and one Y chromosome (XY)
(ii) The gametes receive half of the chromosomes so the male gametes would be 22 + X or 22 + Y and since females have X chromosomes their gametes have 22 + X chromosomes.
(iii) So the sex of the baby is determined by the type of male gamete which fuses with the female.

16. Out of HCl and CH3COOH, which one is a weak acid and why? Describe an activity to support your answer.
CH3COOH is a weak acid when compared to HCl because HCl completely dissociates into ions in solution whereas CH3COOH being weak acid is partially dissociated into ions in solution.
This can be proved by the following activity:
Two iron nails are fitted on a cork and are kept in a 100 mL beaker. The nails  are then connected to the two terminals of a 6-volt battery through a bulb and a switch. Some dilute HCl is poured in the beaker and the current is switched  on. The same experiment is then performed with CH3COOH.
17. Two elements X and Y belong to group 1 and 2 respectively in the same period of periodic table. Compare them with respect to:
(i) the number of valence electrons in their atoms
(ii) their valencies
(iii) metallic character
(iv) the sizes of their atoms
(v) the formulae of their oxides
(vi) the formulae of their chlorides
(i) The number of valence electrons in element X is 1 while in element Y is 2.
(ii) The valency of element X is 1 and that of element Y is 2.
(iii) Element X is more metallic than element Y.
(iv) The size of atom X is more than that of atom Y.
(v) The formula of oxide of element X is X2O and that of element Y is YO.
(vi) The formula of chloride of element X is XCl and that of element Y is YCl2.
18. Draw the ray diagram and also state the position, the relative size and the nature of image formed by a concave mirror when the object is placed at the centre of curvature of the mirror.
19. (i) “The refractive index of diamond is 2.42”. What is the meaning of this statement?
(ii) Name a liquid whose mass density is less than that of water but it is optically denser than water.
(i) “The refractive index of diamond is 2.42.” This means the ratio of sine of angle of incidence to the sine of angle of refraction is equal to 2.42.
(ii) Kerosene has refractive index of 1.44, it’s mass density is less than that of water but it is optically denser than water (kerosene: 1.44 and water: 1.33).
20. What eye defect is hypermetropia? Describe with a ray diagram how this defect of vision can be corrected by using an appropriate lens.
21. (a) List two sexually transmitted disease in each of the following cases:
(i) Bacterial infections
(ii) Viral infections
(b) How may the spread of such diseases be prevented?
(a) Two sexually transmitted disease in each of the following cases are:
(i) Bacterial infections: Syphilis, Gonorrhoea
(ii) Viral infections: AIDS, Genital Herpes
(b) The spread of sexually transmitted diseases can be prevented by using condoms and avoiding multiple partners.
22. Explain Mendel’s law of independent inheritance. Give one example.
Mendel’s law of independent assortment states that
(i) When two pairs of traits are combined in a hybrid, one pair of character segregates independent of the other pair of character.
(ii) In a dihybrid cross between two plants having round yellow (RRYY) and wrinkled green seeds (rryy), four types of gametes (RY, Ry, rY, ry) are produced. Each of these segregate independent of each other, each having a frequency of 25% of the total gametes produced.
23. (a) If the image formed by a lens is diminished in size and erect, for all positions of the object, what type of lens is it?
(b) Name the point on the lens through which a ray of light passes undeviated.
(c) An object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find (i) the position (ii) the magnification and (iii) the nature of the image formed.
(a) If the image formed by a lens is diminished in size and erect, for all positions of the object, then the lens is a concave lens.
(b) The point on the lens through which a ray of light passes undeviated is known as Pole.
(c) 1/f = 1/v + 1/u => 1/20 = 1/v + 1/(-30)  => v = 60cm
The image is formed at a distance of 60 on the other side of the optical centre
(ii) m = -v/u = -60/-20 = 2
(iii)Image formed is inverted.
(a) One-half of a convex lens is covered with a black paper. Will such a lens produce an image of the complete object? Support your answer with a ray diagram.
(b) An object 5 cm high is held 25 cm away from a converging lens of focal length 10 cm.
(i) Draw the ray diagram and
(ii) Calculate the position and size of the image formed.
(iii) What is the nature of the image?
Solution: (a) if one half of the lens is darkened, the image will form. However, the brightness of the image will be less as compared to that of the image formed without wrapping the lens.
(b) (i) Draw the ray diagram
(ii) 1/f = 1/v + 1/u => 1/10 = 1/v + 1/(-25)  => v = 16.67cm
 (iii)  m = -v/u = -hi/h  => hi =  (v xho)/u =  (16.67 x 5)/(-25) = - 3.34 cm
 Negative sign indicates that the image is real & inverted.
24. (a) Draw a diagram of the longitudinal section of a flower and label on it sepal, petal, ovary and stigma.
(b) Write the names of male and female reproductive parts of a flower.
Solution: (b) The male reproductive part of flower is called stamen that consists of filaments and anthers.
The female reproductive part of the flower is pistil that consists of stigma, style and ovary.
(a) What is fragmentation in organisms? Name a multicellular organism which reproduces by this method.
(b) What is regeneration in organism? Describe regeneration in Planaria with the help of a suitable diagram.
Solution: (a) Fragmentation is a mode of asexual reproduction. It is the unintentional cutting up of the body of an organism. Each fragment develops into a new individual. Example: Spirogyra
(b) Regeneration: Regeneration involves the capacity of an organism to give rise to an entire individual from a cut portion. This type of regeneration occurs in Planaria. When Planaria gets cut unintentionally, the cut fragments give rise to a new individual. In this type, active cell division occurs before the replacement. The newly formed mass undergoes differentiation to form specialized cells.
 25. (a) In a tabular form, differentiate between ethanol and ethanoic acid under the following heads:
(i) Physical state   (ii) Taste (iii) NaHCO3 test (iv) Ester test
(b) Write a chemical reaction to show the dehydration of ethanol 
Solution: (a)
(i) Physical state  : Ethanol is a colourless liquid with pleasant odour where as Ethanoic acid is colourless, pungent smelling liquid
(ii) Taste : Ethanol is bitter to taste where as  Ethanoic acid is sour to taste
(iii) NaHCO3 test: Ethanol does not react with sodium bicarbonate where as When ethanoic acid reacts with sodium NaHCO3 with the evolution of carbon dioxide gas.
(iv) Ester test Ethanol on reaction with ethanoic acid in the presence of acid forms ester where as Ethanoic acid on reaction with ethanol in the presence of acid forms ester
(b) Ethanol undergoes dehydration to form ethane.
2CH3CH2 OH ---D-------à 2CH2 = CH2 + 2H2O
(a) What is a soap ? Why are soaps not suitable for washing clothes when the water is hard?
(b) Explain the action of soap in removing an oily spot from a piece of cloth.
(a) A soap can be defined as a sodium or potassium salt ofhigher fatty acids such as oleic acid (C17H33COOH), stearic acid (C17H35COOH), palimitic acid (C15H31COOH), etc.
Soap does not work properly when the water is hard. A soap is a sodium or potassium salt of long chain fatty acids. Hard water contains salts of calcium and magnesium. When soap is added to hard water, calcium and magnesium ions present in water displace sodium or potassium ions from the soap molecules forming an insoluble substance called scum. A lot of soap is wasted in the process.
(b) Cleansing action of soaps:
The oily spot present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the oily spot and remove it from the cloth. Then, the molecules of soap arrange themselves in the form of micelle and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. Hence, the oily spots are easily rinsed away by water.
Section: B
1. A student was given two permanent slides, one of binary fission in amoeba and other of budding in yeast. He was asked to identify any one difference in the nucleus of the two. One such difference, he identified correctly was
(a) Presence of one nucleus in amoeba, two in yeast cell and one in bud.
(b) Presence of two nuclei in centrally constricted amoeba, one in yeast cell and one in its bud.
(c) Presence of two distant nuclei in amoeba, one in yeast cell and two in bud.
(d) Presence of a single nucleus each in amoeba, yeast cell and its attached bud.
Solution: (b)
2. To determine the percentage of water absorbed by raisins, raisins are soaked in water for:
(a) 30 seconds
(b) 10 minutes
(c) 2 to 3 hours
(d) 24 hours
Solution: (c)
3. Raisins are wiped off gently before final weighing with help of
(a) a filter paper
(b) a cotton piece
(c) a cloth piece
(d) a polythene piece
Solution: (a)
4. The step(s) necessary for determining the percentage of water absorbed by raisins is/are:
(a) Raisins should be completely immersed in water
(b) Raisins should be soaked in water for sufficient time
(c) Gently wipe dry the soaked raisins
(d) All of the above steps.
Solution: (d)
5. Mohan obtained a sharp inverted image of a distant tree on the screen placed behind the lens. He then moved the screen and tried to look through the lens in the direction of the object. He would see:
(a) a blurred image on the wall of the laboratory.
(b) an erect image of the tree on the lens.
(c) no image as the screen has been removed
(d) an inverted image of the tree at the focus of the lens.
Solution: (a)
6. For finding the focal length of a convex lens by obtaining the image of a distant object, one should use as the object.
(a) a well lit distant tree
(b) window grill in the class room
(c) any distant tree
(d) a lighted candle kept at the other end of the table.
Solution: (a)
7. To find the focal length of a concave mirror Rahul focuses a distant object with this mirror. The chosen object should be
(a) a tree
(b) a building
(c) a window
(d) the sun
Solution: (d)
8. The colour of an aqueous solution of zinc sulphate as observed in the laboratory is:
(a) Green
(b) Yellow
(c) Blue
(d) Colourless
Solution: (d)
9. To show that zinc is a more active metal than copper, the correct procedure is to:
(a) add dilute nitric acid on strips of both the metals.
(b) observe transmission of heat through strips of zinc and copper.
(c) prepare solution of zinc sulphate and hang strip of copper into it.
(d) prepare solution of copper sulphate and hang strip of zinc into it.
Solution: (d)
10. Acetic acid smells like:
(a) a banana
(b) vinegar
(c) an orange
(d) a lemon
Solution: (b)
11. Acetic acid solution turns:
(a) blue litmus red
(b) red litmus blue
(c) blue litmus colourless
(d) red litmus colourless
Solution: (a)
12. On adding NaHCO3 to acetic acid, a gas is evolved which turns lime water milky due to the formation of:
(1) Calcium bicarbonate
(2) Calcium hydroxide
(3) Calcium carbonate
(4) Calcium acetate
Solution: (c)
13. A yeast cell in which budding occurs was seen to have:
(a) one bud cell
(b) two bud cell
(c) three bud cell
(d) a chain of bud cells
Solution: (a)
14. Rahim recorded the following sets of observations while tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence.

S. No.

(a) I
(b) II
(c) III
(d) IV
Solution: (a) because while light is passing through the rectangular glass slab angle of refraction is less than angle of incidence. 
For more paper :  CBSE X Sample Paper 2014