7[1]. light assignment

7/28/2019 7[1]. Light Assignment

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SCIENCE ASSIGNMENT X STEPS A TCY Program _________________________________________________________________________________

STEPS____________________________________________________________G e t f r e e n o t e s f o r C l a s s X a n d I X o n

w w w . t c y o n l i n e . c o m

1

ASSIGNMENT ON LIGHT

TYPE A

REFLECTION OF LIGHT

Plane mirror

1. What is the focal length and radius of curvature of a plane mirror?

2. What is the nature of image formed by a plane mirror?

3. What is the magnification of a plane mirror?

4. An object is placed in front of a plane mirror at a distance u. Calculate distance between the image and

the object?

5. Write the properties of a plane mirror.

6. Write two uses of a plane mirror.7. Using ray diagram, explain the image formation in a plane mirror.

8. Leela while combing estimated that she is about 1 m apart from the mirror. What will be distance

between her image and her?

Spherical mirrors

1. A concave mirror is cut from a sphere whose radius is 15 cm. What will be the focal length of the mirror?

2. An object is 20 cm apart from the focus of a concave mirror. Where would the image of the object form,

if focal length of mirror is 20 cm?

3. A convex mirror is 20 cm apart from a candle and its focal length is 10 cm. What will be the nature and

position of the image formed?

4. A motorcyclist sees another motorcyclist behind him in his rear view mirror, of focal length 50 cm. Both

are moving with the same speed and are separated by a distance of 5 m. What will be the position of the

image of the other motorcyclist?

5. Two circular portions were cut from a spherical mirror of radius of curvature 40 cm. The radii of two

circular portions are 10 cm and 12 cm respectively. Which of the circular portions has the greater radius

of curvature?

6. Initially, an object placed at 10 cm from a concave mirror of focal length 20 cm is displaced by 5 cm away

from the mirror. What will be the change in position of the image?

7. A candle of height 10 cm is placed 15 cm from a convex mirror of focal length 10 cm. What will be the

height of image of the candle?

8. An inverted image of a boy is received on a screen 200 cm from a concave mirror of focal length 100 cm.

What is the position of the boy?


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9. A convex mirror is lying on a horizontal plane and distance between the ceiling fan and the mirror is 5 m.

How deep image of the fan will be formed, if focal length of the mirror is 0.5 m.

10. If a matchstick of height 3 cm is placed 4 cm from the pole of a concave mirror of focal length 10 cm,

what will be the size of image?

11. A source of light is placed 10 cm from the pole of a convex mirror of focal length 15 cm. What will be the

magnification of the mirror?

12. A convex mirror has a radius of curvature 20 cm. An object 3 cm tall is placed 8cm in front of the mirror.

Locate the image of the object with the help of a ray diagram. Also, discuss the nature and the size of

image formed. How will the position of image change if the object is placed?

(A) 10 cm from the mirror (B) 15 cm from the mirror

(C) 20 cm from the mirror (D) 25 cm from the mirror

13. How can a concave mirror/convex mirror be used to produce a virtual image?

14. If the image formed by a mirror is upright and reduced in size, what type of mirror is used?

15. A concave mirror is used to create a beam of light with parallel rays. What will be the position of the light

source?

16. State whether the following statements are true/false for virtual image.

(i) Virtual image is always upright.

(ii) Virtual image can be located in front of the mirror.

(iii) Virtual image is always formed by plane and convex mirror but for a concave mirror, virtual image is

formed only when the object is placed between the focal point and the pole of the mirror.

(iv) Virtual image is formed only when the reflected light rays diverge.

(v) Virtual image can be of any size.

17. State whether the following statements are true/false for real image.

(i) Real image can be either upright or inverted.

(ii) Real image can be of any size.

(iii) Real image are always located behind the mirror.

(iv) Real image can be formed by convex and plane mirror.

(v) Real image can be obtained on the screen.

18. Discuss the characteristics of an image when

(i) f < u < R for a concave mirror(ii) u < f for a concave mirror

(iii) u > R for a concave mirror

Where; f is the focal length, u is the object position, v is the position of image, and R is the radius of

curvature of the mirror.

19. For mirrors, the sign of magnification is same as that of sign of_____.


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20. What are the various characteristics of concave and convex mirror?

21. Is the sign of magnification always negative for concave mirror?

22. Why is the concave mirror used by the dentists?

23. Differentiate between real image and virtual image.

24. When will the image formed by a concave mirror be virtual?

25. Which mirror is curved outward?

26. Which mirror is curved inward?

27. What will be the position of an object for which the image formed by a concave mirror is smaller than

the size of the object?

28. At what multiple of focal length, the size of image is same as that of the object?

29. Complete the table below:

I II III IV V VI VII

Type Concave Concave Concave Convex Concave Concave Concave

f(cm) 15 10 15

R (cm) 20 25

u (cm) 25 10 20 15 40 6

v (cm) 35

M 3 +2

Real Image

Upright image

30. A concave mirror of focal length 20 cm forms a real image at a distance of 30 cm from the mirror. What

will be the position of the object?

31. An object is placed in front of a concave mirror at a distance twice the focal length of the mirror. If the

image is formed at a distance of 30 cm from the mirror, calculate the focal length of the mirror and

position of the object.

32. Two times diminished image is formed when an object is placed at a distance of 10 cm from the curved

mirror. What will be the focal length of the mirror, the nature and position of the image so formed?

33. Three times diminished image is formed when an object is placed in front of a curved mirror of focal

length 10 cm. Find the nature and position of image so formed.

34. Radius of curvature of a curved mirror is 30 cm. A real image is formed at a distance 20 cm from the

mirror. How many times the imaged formed is magnified?

35. Differentiate between concave and convex mirrors.


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36. An inverted image formed by a concave mirror is4

3 th as large as the object, which is positioned 20 cm in

front of mirror. Calculate the focal length of the mirror.

37. Write two uses of each, the convex and the concave mirrors.

TYPEB

REFRACTION OF LIGHT

LENS

1. Why is convex lens used in lighting the streets in the evening?

2. A student is having two lens of equal power. He combined them and power of combination was zero.

What was the nature of two lenses?

3. An object of height 5 cm is placed in front of a diverging lens at a distance of 40 cm from the lens. If the

image is formed 10 cm in front of the lens, then calculate the focal length of the mirror and size of the

image so formed.

4. A man of height 1.5 m is standing at a distance of 2 m from a convex lens of focal length 50 cm. What

will be height of the image?

5. Two convex lenses of focal length 20 cm and 40 cm respectively are placed in contact with each other.

What will be the focal length of combination?

6. An object is placed 50 cm from a concave lens of power 2 diopter. Both the object and the lens are

moved towards each other by a distance of 5 cm. Where will the final image be formed?

7. An object is placed 15 cm from combination of a concave and a convex lens of power 10 D and 5 D

respectively. Where will the image be formed?

8. A virtual image thrice as big as the object is formed by a convex lens when the object is placed at 15 cm

from the lens. Image formed will be as big as the object if the object is placed at a distance of________.

9. Focal length of a lens is increased by4

3 th of its initial value. What will be new power of lens, if P is its

initial power?

10. Draw a ray diagram for an object placed between the focus and the curvature of a convex lens.

11. Distinguish between convex and concave lens.

12. Write two uses of each, the concave and the convex lens.13. An object is placed at distance of 10 cm from a convex lens of power 4 diopter. What will be the

magnification of the lens?

14. What are the various sign conventions used in lenses?

15. Write the lens formula in terms of radius of curvature.


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16. Prove the following relations for lenses

(A) =f v/(1m) (B) hi/ho = u/(uf)

17. An object is placed 15 cm from the convex lens of radius of curvature 10 cm. If the object is displaced 5

cm towards the lens, what will be the shift in position of image?

18. A 5 cm tall object is placed at distance of 50 cm in front of a diverging lens of focal length 30 cm. Find

the size of the image formed.

19. How is power of a lens related to its focal length? What are its units?

20. An object of height 0.06 m is viewed through a diverging lens of power 20 diopters. The image is

observed to be 0.01 m in height. How much is the object distance from the lens.

21. A spherical lens of focal length 15 cm forms a virtual image when an object is placed at a distance of 10

cm from the lens. Find the position of the image formed and the magnification of the lens.

Refractive Index

22. Refractive index of Diamond is 2.4. What will be speed of light in diamond?

23. White light falls on a glass slab of refractive index 1.33 at an incident angle 25. At what angle will the

white light refract?

24. A coin placed at the bottom of a glass of water, appears slightly raised above its actual position. Why?

25. Any straight partly dipped in the water, appears bent. Why?

26. During sunset or sunrise, sun appears reddish. Why?

27. What is the phenomenon involved behind the blue colour of the sky.

28. The refractive index of diamond is 2.4 and that of water is 1.5. What will be the refractive index of water

with respect to diamond and diamond with respect to water?

29. The refractive index of lead sulphide with respect to zircon is 0.49. If the speed of light in lead sulphide is

0.8 108 m/s, calculate the speed of light in zircon.

30. Which of the following is the unit of refractive index?

(A) g/cm3 (B) cm3/g (C) candela (D) no units

31. When light passes through an optical medium, which of the following quantities changes?

(A) Frequency and speed of light (B) Wavelength and speed of light

(C) Frequency and speed of light (D) Only speed of light

32. Define Snells law.

33. A Ray of light enters a glass slab at an angle of 30 and refract at 22. What will be velocity of light in the

glass slab?


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Dispersion and Total internal reflection

34. How is total internal reflection related to critical angle?

35. What is the lateral displacement of an incident ray when it is refracted through a rectangular glass slab?

How will the lateral displacement be effected, if the dimensions of the glass slab are increased?

36. Why is dispersion possible with a prism only, but not with a rectangular slab?

37. Define laws of reflection and refraction. Distinguish between reflection and refraction.

38. Define total internal reflection. Name the natural phenomenon, which can be explained by internal

reflection.

39. Write relation between critical angle and refractive index.

40. Define dispersion and write relation for angle of dispersion.

41. Which of following explains occurrence of Rainbow?

(A) Total internal reflection (B) Refraction

(C) Snells law (D) Dispersion

42. For three media refractive indices are given as u1 > u2 > u3. Which of following sequence is correct for

critical angle?

(A) C1 > C2 > C3 (B) C1 = C2 = C3 (C) C1 < C2 < C3 (D)1C

1=

2C

1=

3C

1

43. Define critical angle.


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TYPE A

Spherical mirrors

1. 7.5 cm 2. 3. 6.7 cm, virtual 4. 11500 cm

5. same for both 6. 3

40cm 7.

3

12cm 8. 200 cm

9. 0.45 m 10. 5 cm 11. 0.6 cm 19. v

29.

I II III IV V VI VII

Type Concave Concave Concave Convex Concave Concave Concave

f(cm) 15 10 2

25 +10 15 30

12

R (cm) 30 20 25 +20 30 60 24

u (cm) 4

105 25 10 20 15 40 6

v (cm) 35 3

50 +50 +

3

20 120 +12

M 3

43

2 +5 +

3

1 3 +2

Real Image

Upright image

30. 60 cm 31. 15 cm, 30 cm 32. 10 cm, virtual, 5 cm

33. virtual,3

20cm 34.

3

136.

7

60cm

TYPE B

lens

3. 3

40cm,

4

5cm 4. 0.5 m 5.

3

40cm 6.

9

200cm

7. 7

60cm 8. 45 cm 9.

7

4P 13.

3

5

17. 2.5 cm 18. 1. 875 cm 20. 0.25 m

21. For convex lens: v = 30 cm, m = 3 For concave lens: v = 6 cm, m =5

3

22. 1.25 108 m/s 23. 18.5 28. 1.6, 0.625 29. 1.6 108 m/s

30. (D) 31. (B) 33. 2.25 108 m/s 41. (A)

42. (C)

ANSWER KEY

7[1]. light assignment

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