Class 10th Physics
CHAPTER - 10
LIGHT – REFLECTION AND REFRACTION
*NUMERICALS BASED ON CONVEX AND CONCAVE MIRROR :
Que 1. Find the focal length of a convex mirror of radius of curvature 1m.
Que 2. Focal length of a convex mirror is 50 cm. What is its radius of curvature?
Que 3. Radius of curvature of a concave mirror is 25 cm. What is its focal length?
Que 4. A concave mirror produces 10 cm long image of an object of height of 2cm. What is the magnification produced?
Que 5. An object 1 cm high is held near a concave mirror of magnification 10. How tall will be the image?
Que 6. An object 4 cm in size is placed at a distance of 25 cm from a concave mirror of focal length 15 cm. Find the position, nature and height of the image.
Que 7. A converging mirror forms a real image of height 4 cm, of an object of height 1 cm placed 20 cm away from the mirror. Calculate the image distance. What is the focal length of the mirror?
Que 8. A 4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of the image and the magnification. Describe what happens as the needle is moved farther from the mirror.
Que 9. An arrow 2.5 cm high is placed at a distance of 25 cm from a diverging mirror of focal length 20 cm., Find the nature, position and size of the image formed.
Que 10. The image formed by a convex mirror of focal length 20cm is a quarter of the object. What is the distance of the object from the mirror?
Que 11. Find the size, nature and position of image formed by a concave mirror, when an object of size 1cm is placed at a distance of 15cm. Given focal length of mirror is 10cm.
Que 12. An object 2cm high is placed at a distance of 16cm from a concave mirror, which produces 3cm high inverted image. What is the focal length of the mirror? Also, find the position of the image.
Que 13. An erect image 3 times the size of the object is obtained with a concave mirror of radius of curvature 36cm. What is the position of the object?
Que 14. A 2.5cm candle is placed 12 cm away from a convex mirror of focal length 30cm. Give the location of the image and the magnification.
Que 15. An object is placed in front of a concave mirror of focal length 20cm. The image formed is 3 times the size of the object. Calculate two possible distances of the object from the mirror.
Que 16. The image formed by a convex mirror is virtual, erect and smaller in size. Illustrate with figure.
Que 17. A concave mirror produces a real image 10mm tall, of an object 2.5mm tall placed at 5cm from the mirror. Calculate focal length of the mirror and the position of the image.
Que 18. An object is placed at a large distance in front of a convex mirror of radius of curvature 40cm. How far is the image behind the mirror?
Que 19. An object is placed 15cm from a convex mirror of radius of curvature 90cm. Calculate position of the image and its magnification.
Que 20. The image formed by a convex mirror of focal length 30cm is a quarter of the object. What is the distance of the object from the mirror?
Que 21. When an object is placed at a distance of 60cm from a convex mirror, the magnification produced is 1/2. Where should the object be place to get a magnification of 1/3?
Que 22. An object is placed 18cm front of a mirror. If the image is formed at 4cm to the right of the mirror. Calculate its focal length. Is the mirror convex or concave? What is the nature of the image? What is the radius of curvature of the mirror?
Que 23. A convex mirror used for rear view on an automobile has a radius of curvature of 3m. If a bus is located at 5m from this mirror, find the position, nature and magnification of the image.
Que 24. An object 3cm high is held at a distance of 50cm from a diverging mirror of focal length 25cm. Find the nature, position and size of the image formed.
Que 25. An converging mirror of focal length 20cm forms an image which is two times the size of the object. Calculate two possible distances of the object from the mirror.
26. The linear magnification of a convex mirror of focal length 15cm is 1/3. What is the distance of the object from the focus of the mirror?
27. The focal length of a convex mirror is 12.5 cm. How far is its centre of curvature (i) from the pole (ii) from the focus.
28. Find the focal length of a concave mirror that produces four times larger real image of an object held at 5cm from the mirror.
29. An object is held at 30cm in front of a convex mirror of focal length 15cm. At what distance from the convex mirror should a plane mirror be held so that images in the two images coincide with each other?
30. Draw any three ray diagrams to show how the size and nature of image of an object change when it move from centre of curvature of concave mirror towards the pole of the mirror.
REFRACTION OF LIGHT
1. Light travels through water with a speed of 2.25 x 108 m/s. What is the refractive index of water?
2. Light travels from rarer medium 1 to a denser medium 2. The angle of incident and refraction are respectively 450 and 300 . Calculate the (i) refractive index of second medium with respect to the first medium and (ii) refractive index of medium 1 with respect to the medium 2.
3. A pond of depth 20cm is filled with water of refractive index 4/3. Calculate apparent depth of the tank when viewed normally.
4. How much time will light take to cross 2mm thick glass pane if refractive index of glasses is 3/2?
5. Calculate speed of light in water of refractive index 4/3.
6. A ray of light passes from air to glass (n = 1.5) at an angle of 300 . Calculate the angle of refraction.
7. A ray of light is incident on a glass slab at an angle of 450 . If refractive index of glass be 1.6, what is the angle of refraction?
8. The refractive index of diamond is 2.47 and that of glass is 1.51. How much faster does light travel in glass than in diamond?
9. The refractive index of glycerine is 1.46. What is the speed of light in air in air if its speed in glecerine is 2.05 x 108 m/s?
10. The refractive index of glass is 1.6 and that of diamond is 2.4. Calculate (i) refractive index of diamond with respect to glass and (ii) refractive index of glass with respect to diamond.
11. A ray of light is travelling from glass to air. The angle of incidence in glass is 300 and angle of refraction in air is 600 . What is the refractive index of glass w.r.t air?
12. A ray of light is travelling from air to water. What is the angle of incidence in air, if angle of refraction in water is 450 ? Take refractive index of water = 1.32
13. A water tank appears to be 4 m deep when viewed from the top. If refractive index of water is 4/3, what is the actual depth of the tank?
14. What is the real depth of a swimming pool when its bottom appears to be raised by 1m? Given refractive index of water is 4/3.
15. A jar 15 cm long is filled with a transparent liquid. When viewed from the top, its bottom appears to be 12cm below. What is the refractive index of the liquid?
NUMERICALS BASED ON CONVEX LENS
1. A convex lens of focal length 10cm is placed at a distance of 12cm from a wall. How far from the lens should an object be placed so as to form its real image on the wall?
2. If an object of 7cm height is placed at a distance of 12cm from a convex lens of focal length 8cm, find the position, nature and height of the image.
3. An object 4 cm high is placed at a distance of 10cm from a convex lens of focal length 20cm. Find the position, nature and size of the image.
4. A small object is so placed in front of a convex lens of 5 cm focal length that a virtual image is formed at a distance of 25cm. Find the magnification.
5. Find the position and nature of the image of an object 5cm high and 10cm in front of a convex lens of focal length 6cm.
6. Calculate the focal length of a convex lens, which produces a virtual image at a distance of 50cm of an object placed 20cm in front of it.
7. An object is placed at a distance of 100 cm from a converging lens of focal length 40cm. What is the nature and position of the image?
8. A convex lens produces an inverted image magnified three times of an object at a distance of 15 cm from it. Calculate focal length of the lens.
9. An object placed 4cm in front of a converging lens produces a real image 12cm from the lens. What is the magnification of the image? What is the focal length of the lens? Also draw the ray diagram to show the formation of the image.
10. A lens of focal length 20cm is used to produce a ten times magnified image of a film slide on a screen. How far must the slide be placed from the lens?
11. Determine how far an object must be placed in front of a converging lens of focal length 10cm in order to produce an erect image of linear magnification 4.
12. A convex lens of focal length 6cm is held 4cm from a newspaper, which has print 0.5cm high. By calculation, determine the size and nature of the image produced.
13. A convex lens of focal length 0.10m is used to form a magnified image of an object of height 5mm placed at a distance of 0.08m from the lens. Find the position, nature and size of the image.
14. An erect image 2cm high is formed 12cm from a lens, the object being 0.5cm high. Find the focal length of the lens.
15. The filament of a lamp is 80 cm from a screen and a converging lens forms an image of it on a screen, magnified three times. Find the distance of the lens from the filament and the focal length of the lens.
16. An object 2cm tall is placed on the axis of a convex lens of focal length 5cm at a distance of 10cm from the optical centre of the lens. Find the nature, position and size of the image formed. Which case of image formation by convex lenses is illustrated by this example?
17. A converging lens of focal length 5cm is placed at a distance of 20cm from a screen. How far from the lens should an object be placed so as to form its real image on the screen?
18. An object 5cm high is held 25cm away from a converging lens of focal length 10cm. Find the position, size and nature of the image formed. Also draw the ray diagram.
19. At what distance should an object be placed from a convex lens of focal length 18cm to obtain an image at 24cm from it on the other side? What will be the magnification produced in this case?
20. The magnification produced by a spherical lens is +2.5. What is the nature of image and lens?
21. What is the nature of the image formed by a convex lens if the magnification produced by a convex lens is +3?
22. What is the nature of the image formed by a convex lens if the magnification produced by a convex lens is –0.5?
23. What is the position of image when an object is placed at a distance of 10cm from a convex lens of focal length 10cm?
24. Describe the nature of the image formed when an object is placed at a distance of 30cm from a convex lens of focal length 15cm.
25. At what distance from a converging lens of focal length 12cm must an object be placed in order that an image of magnification 1 will be produced?
NUMERICALS BASED ON CONCAVE LENS
1. A concave lens produces an image 20cm from the lens of an object placed 30cm from the lens. Calculate the focal length of the lens.
2. The magnification of a spherical lens is +0.5. What is the nature of lens and image?
3. If an object is placed at a distance of 50cm from a concave lens of focal length 20cm, find the position, nature and height of the image.
4. An object is placed at a distance of 4 cm from a concave lens of focal length 12cm. Find the position and nature of the image.
5. An object is placed at a distance of 50cm from a concave lens produces a virtual image at a distance of 10 cm in front of the lens. Draw a diagram to show the formation of image. Calculate focal length of the lens and magnification produced.
6. A 50 cm tall object is at a very large distance from a diverging lens. A virtual, erect and diminished image of the object is formed at a distance of 20 cm in front of the lens. How much is the focal length of the lens?
7. A concave lens of focal length 15cm forms an image 10cm from the lens. How far is the object placed from the lens? Draw the ray diagram.
8. An object 60cm from a lens gives a virtual image at a distance of 20cm in front of the lens. What is the focal length of the lens? Is the lens converging or diverging? Give reasons for your answer.
9. A concave lens of 20 cm focal length forms an image 15cm from the lens. Compute the object distance.
10. A concave lens has focal length 15 cm. At what distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also find the magnification produced by the lens.
11. Calculate the image distance for an object of height 12 mm at a distance of 0.20 m from a concave lens of focal length 0.30m and state the nature and size of the image.
12. A concave lens has focal length of 20cm. At what distance from the lens a 5cm tall object be placed so that it forms an image at 15cm from the lens? Also calculate the size of the image formed.
13. An object is placed 20cm from (a) a converging lens and (b) a diverging lens of focal length 15cm. Calculate the image position and magnification in each case.
14. A 2.0 cm tall object is placed 40cm from a diverging lens of focal length 15 cm. Find the position and size of the image.
15. Find the position and size of the virtual image formed when an object 2 cm tall is placed 20cm from (a) diverging lens of focal length 40cm and (b) converging lens of focal length 40 cm.
16. The magnification produced by a spherical lens is +0.75. What is the nature of image and lens?
17. The magnification produced by a spherical lens and a spherical mirror is +0.8. What is the nature of lens and mirror?
18. The magnification produced by a spherical lens and a spherical mirror is +2.0. What is the nature of lens and mirror?
19. The lens A produces a magnification of –0.6 whereas lens b produces magnification of +0.6. What is the nature of lens A and B.
20. An object is 2m from a lens which forms an erect image one-fourth (exactly) the size of the object. Determine the focal length of the lens. What type of the lens is this?
NUMERICALS ON POWER OF LENS
1. A concave lens produces an image 20cm from the lens of an object placed 30cm from the lens. Calculate the power of the lens.
2. A convex lens is of focal length 10 cm. What is its power?
3. A person having a myopia eye uses a concave lens of focal length 50cm. What is the power of the lens?
4. A thin lens has a focal length of –25cm. What is the power of the lens and what is its nature?
5. A lens has a power of –2.5 D. What is the focal length and nature of the lens?
6. Find the power of a concave lens of focal length 2 m.
7. A convex lens forms a real and inverted image of needle at a distance of 50cm from the lens. If the image is of the same size as the needle, where is the needle placed in front of the lens? Also, find the power of the lens.
8. Two thin lenses of power +3.5 D and –2.5 D are placed in contact. Find the power and focal length of the lens combination.
9. A doctor has prescribed a corrective lens of power –1.5 D. Find the focal length of the lens. Is the prescribed lens is diverging or converging?
10. A concave lens of focal length 25 cm and a convex lens of focal length 20 cm are placed in contact with each other. What is the power of this combination? Also, calculate focal length of the combination.
11. A convex lens of focal length 20 cm is placed in contact with a concave lens of focal length 10cm. What is the focal length and power of the combination?
12. An object is placed at a distance of 50cm from a concave lens of focal length 30cm. Find the nature and position of the image.
13. An object of height 2 cm is placed at a distance of 15cm in front of a concave lens of power –10D. Find the size of the image.
14. A convergent lens of power 8D is combined with a divergent lens of power –10D. Calculate focal length of the combination.
15. A concave lens is kept in contact with a convex lens of focal length 20cm. The combination works as a converging lens of focal length 100cm. Calculate power of concave lens.
16. Find the focal length and nature of lens which should be placed in contact with a lens of focal length 10 cm so that the power of the combination becomes 5D.
17. A convex lens of power 3D is held in contact with a concave lens of power – 1 D. A parallel beam of light is made to fall on the combination. At what distance from the combination will the bean ge5t focussed?
18. A convex lens of focal length 25cm and a concave lens of focal length 10cm are placed in close contact with one another.
a). What is the power of the combination?
b). What is the focal length of the combination?
c). Is this combination converging or diverging?
19. The power of a combination of two lenses X and Y is 5D. If the focal length of lens X be 15 cm, then
a). calculate the focal length of lens Y.
b). State the nature of the lens Y.
20. Two lenses A and B have focal lengths of +20cm and – 10 cm, respectively.
a). What is the nature of lens A and lens B?
b). What is the power of lens A and lens B? What is the power of the combination if lenses A and B are held close together?
CHAPTER - 10
LIGHT – REFLECTION AND REFRACTION
ASSIGNMENT QUESTIONS
1. Define refraction.
2. Define refractive index.
3. What is the unit of refractive index?
4. List out the factors on which the refractive index of a medium depends.
5. Define angle of incidence.
6. What is the angle of incidence if a ray of light is incident normal to the surface separating the two media?
7. What is a lens?
8. What is a concave lens?
9. What is the nature of the focus of a concave lens?
10. What type of image is formed by a concave lens?
11. A thin lens has a focal length f = -12 cm. Is it convex or concave lens?
12. A lens forms an erect image for all positions of the object in front of it. Is the lens convex or concave?
13. Where should an object be placed so that a real and inverted image of same size is obtained using a convex lens?
14. Write the relation between u,v and f of a thin lens.
15. What is the sign of u, v and f for a convex lens according to Cartesian sign convention?
16. An object of height 1m is placed at a distance of 2f from a convex lens. What is the height of the image formed?
17. Define power.
18. What is least distance of distinct vision?
19. What happens when a ray of light passes through the optical centre of a lens?
20. State the laws of refraction.
21. Diagrammatically represent the refraction of light through a rectangular glass slab.
22. Define convex lens. Why is it referred to as converging lens?
23. Draw a diagram to show the second principal focus of a convex lens.
24. Distinguish between a convex and a concave lens.
25. Draw a ray diagram to show the refraction of light when it passes through the optic centre of a convex lens.
26. List out the uses of convex lenses.
27. With the help of a ray diagram show how an object gets magnified in a simple microscope.
28. Define the power of a lens. What is its unit?
29. With the help of a diagram explain how light gets refracted when it passes through a rectangular glass slab.
30. An object is placed at a distance of 50 cm from a concave lens of focal length 20 cm. Find the nature and position of the image.
31. An object is placed 50 cm from a lens which produces a virtual image at a distance of 10 cm in front of the lens. Draw a diagram to show the formation of image and calculate the focal length of the lens.
32. An object of height 4 cm is placed at a distance of 10 cm from a convex lens of focal length 20 cm. Find the position, nature and size of the image.
33. What is the power of a lens having a focal length of a) 50 cm b) -50cm
34. Draw a ray diagram to show the position and nature of the image formed by a convex lens when the object is placed a) at 2F1 b) between F1 and 2F1 c) beyond 2F1
35. State and verify Snell's law.
36. The bending of a beam of light when it passes obliquely from one medium to another is known as _______.
1. reflection 2. refraction
3. dispersion 4. deviation
37. The part of the lens through which the ray of light passes without suffering deviation is called ________.
1. optical centre 2. focus
3. centre of curvature 4. pole
38. Convex lens always gives a real image if the object is situated beyond _______.
1. optical centre 2. centre of curvature
3. Focus 4. radius of curvature
39. Parallel rays of light entering a convex lens always converge at _______.
1. centre of curvature 2. the principal focus
3. optical centre 4. the focal plane
40. Where should an object be placed so that a real and inverted image of the same size is obtained, using a convex lens?
1. Between O and F
2. At F
3. At 2 F
4. At infinity
41. SI unit of the power of a lens is ___________.
1. dioptre 2. cm
3. metre 4. watt
42. 1 D is the power of the lens of focal length of ______ cm.
1. 100
2. 10
3. 1/100
4. 1/10
43. In a simple microscope lens used is __________.
1. biconvex
2. biconcave
3. plano convex
4. cylindrical
44. Reciprocal of focal length in metres is known as the ______ of a lens.
1. focus
2. power
3. power of accommodation
4. far point
45. A convex lens is called _________.
1. converging lens
2. diverging lens
3. both converging and diverging lens
4. refracting lens
46. A positive magnification greater than unity indicates _____________________.
1. real image
2. virtual image
3. neither real not virtual image
4. distorted image
47. The power of a convex lens of focal length 50 cm is ______.
1. + 2D
2. - 2D
3. 50 D
4. - 5D
48. The focal length of a lens whose power is -1.5 D is _______.
1. -66.66 cm
2. + 1.5 m
3. + 66.66 cm
4. -1.5 m
49. Real images formed by single convex lenses are always ________________.
1. on the same side of the lens as the object
2. Inverted
3. Erect
4. smaller than the object
50. An object is placed 12 cm from a convex lens whose focal length is 10 cm. The image must be.
1. virtual and enlarged
2. virtual and reduced in size
3. real and reduced in size
4. real and enlarged
51. When a person uses a convex lens as a simple magnifying glass, the object must be placed at a distance.
1. less than one focal length
2. more than one focal length
3. less than twice the focal length
4. more than twice the focal length
52. The image produced by a concave lens is ________.
1. always virtual and enlarged
2. always virtual and reduced in size
3. always real
4. sometimes real, sometimes virtual
53. A virtual image is formed by _______.
1. a slide projector in a cinema hall
2. the ordinary camera
3. a simple microscope
4. Telescope
54. An object is placed 25 cm from a convex lens whose focal length is 10 cm. The image distance is ________ cm.
1. 50 cm
2. 16.66 cm
3. 6.66 cm
4. 10 cm
55. The least distance of distinct vision is ______.
1. 25 cm
2. 25 m 3. 0.25 cm 4. 2.5 m
56. A convex lens has a focal length of 20 cm. Its power in dioptres is ___________.
1. 2
2. 5
3. 0.5
4. 0.2
57. An object is placed before a concave lens. The image formed _____________-.
1. is always erect
2. may be erect or inverted
3. is always inverted
4. is always real
58. A ray of light travels from a medium of refractive index n1 to a medium of refractive index n2. If angle of incidence is i and the angle of refraction is r, then sin sin i r is equal to
1. n1
2. n2
3. n21
4. n12
59. Two thin lenses of power +5 D and -2 D are placed in contact with each other. Focal length of the combination is
1. +3 m
2. -3 m
3. 0.33 m
4. -0.33 m
61. An object is placed between two plane mirrors inclined at an angle of 45° to each other. How many images do you expect to see?
62. How can an inverted image of an object be obtained with a plane mirror?
63. How many images of himself can an observer see in a room whose ceiling and two adjacent walls are mirrors?
64. A convex mirror is held in water. What should be the change in its focal length?
65. If the light from the Sun subtend an angle Q at the pole of a concave mirror of focal length f, where will it converge? Also find the diameter of the image. Draw the necessary ray diagram.
66. When does Snell’s law of refraction fail?
67. How does the frequency of a beam of ultraviolet light changes when it goes from air to glass?
68. State two conditions under which a ray of light suffering refraction from medium 1 to medium 2 does not undergo any change in direction
69. Name the factor on which lateral shift produced by glass slab depends?
70. A glass lens is immersed in water. How is the power of the lens affected?
71. Why is the power of a lens is measured as reciprocal of focal length? Give reason.
72. A convex lens is made of a material of refractive index m1 when placed in a medium of refractive index m2, behaves as a diverging lens. How are m1 and m2 related?
73. An object is held at a distance of 60 cm from a convex mirror of focal length 20 cm. At what distance from the mirror, should a plane mirror be held so that images in the two mirrors coincide?(ans. 22.5 cm)
74. How do you find the rough focal length of a convex lens? Is the same method applicable to a concave lens?
75. Which factors determines the focal length of a lens?
76. The formula for linear magnification of a spherical mirror is m=h’/h = -v/u. What determines the sign of m? What is the significance of this sign?
77. A convex lens made of material of refractive index n2 is kept in a medium of
refractive index n1. A parallel beam of light is incident on the lens. Compare the
path of rays of light emerging from the convex lens if (i)n1
CHAPTER - 11
THE HUMAN EYE AND THE COLOURFUL WORLD
1. A man can read the number of a distant bus clearly but he finds difficulty in reading a book. From which defect of the eye is suffering from?
2. What type of spectacles should be worn by a person having the defects of myopia as well as hypermetropia? How does it help?
3. The sun near the horizon appears flattened at the sun set and sun rise. Explain why.
4. Explain why and when the sun is overhead at noon it appears white
5. A boy uses spectacles of focal length -50 cm. Name the defect of vision he is suffering from. Compute the power of this lens.
6. Give the meaning of the term ‚ VIBGYOR‛ with which phenomenon is it connected?
7. Explain the following terms connected with the eye. (i) Ciliary muscles (ii) Accommodation.
8. What is meant by spectrum of white light?
9. What will be colour of the sky in the absence of atmosphere?
10. Why are the traffic light signals (or danger signals) of red colour?
11. Why does the sky appear dark and black to an astronaut instead of blue?
12. Explain why, when the sun is overhead at noon, it appears white?
13. What is Atmospheric Refraction?
14. A person with myopic eye cannot see objects beyond 1.2metre distinctly. What should be the nature of corrective lenses to restore proper vision?
15. The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
16. The far point of myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to enable him to see very distant objects distinctly?
17. The far point of a myopic person is 150 cm in front the eye. Calculate the focal length and power of a lens required to enable him to see distant objects clearly.
18. How is the eye lens held in its position?
19. What is meant by near point?
20. What is meant by least distance of distinct vision?
21. Which part of the eye controls the amount of the light entering the eye?
22. Which liquid fills the space behind the cornea?
23. Why is blind spot so called?
24. What is meant by the accommodation of the eye?
25. What is the least distance of distinct vision of a normal human eye?
26. Name the defects of vision of human eye?
27. What is the other name of near sightedness?
28. Where is the image formed in an eye suffering from near sightedness?
29. What is the other name of long sightedness?
30. Where is the image formed in an eye suffering from long sightedness?
31. How is long sightedness corrected?
32. A person has to use a concave lens in his spectacles. What defect of vision is he suffering from?
33. What is the other name of Presbyopia?
34. What is the twinkling of stars due to?
35. Give one example of source of white light.
36. Which scientist first explains the dispersion of light?
37. Name the delicate membrane in the eye having enormous number of light sensitive cells.
38. What kind of lens is used in the spectacles of a person suffering from Myopia (near sightedness)?
39. On what factor the colour of the scattered light depends?
40. What is a function of choroids?
41. Why does sky appear blue on a clear sky?
42. What happens to the lens and the ciliary muscles when you are looking at nearby objects?
43. In an experiment the image of a distant object formed by a concave mirror is obtained on a screen. To determine the focal length of the mirror, you need to measure the distance between the:- (a) Mirror and the screen (b) Mirror and the object (c) Object and the screen (d) Mirror and the screen and also between the object and the screen.
44. The image formed by concave mirror is real. The position of the screen should be (a) behind the mirror (b) on the same side of object between focus and infinity (c) on the same side of object between focus and pole(d) none of these
45. In the experiment to determine focal length of a convex lens, a student obtained a sharp inverted image of a distant tree on the screen behind the lens. She then removed the screen and looked through the lens in the direction of the object. She will see:- (a) An inverted image of the tree at the focus. (b) No image as the screen has been removed. (c) A blurred image on the wall of the laboratory. (d) An erect image of the tree on the lens.
46. While performing the experiment for determination of focal length of a convex lens by using the sun as a distant object a student could not find a screen with stand. Which one of the following methods he should adopt safely? He should see:- (a) The image of sun directly through convex lens. (b) Focus the image of sun on his hand (c) Focus the image of sun on his nylon shirt. (d) Focus the image of sun on the wall of the room.
47. In an experiment to determine the focal length of a convex lens, the image of a distant tree is obtained on the screen. To determine the focal length of the lens, you are required to measure the distance between the :- (a) Lens and the tree only (b) Lens and the screen only (c) Screen and the tree only (d) Screen and the tree and also between the screen and the lens
48. For performing an experiment, a student was asked to choose one concave mirror and one convex lens from a lot of mirrors and lenses of different kinds. The correct procedure adopted by her will be :- (a) To choose a mirror and lens which can form an enlarged and inverted image of an object. (b) To choose a mirror which can form a diminished and erect image and a lens which can form an enlarged and erect image of the object. (c) To choose a mirror and lens which can form an enlarged and erect image of an object. (d) To choose a mirror and a lens which can form a diminished and erect image of an object.
SHORT ANSWER QUESTIONS
15. Draw ray diagrams each showing (i) myopic eye and (ii) hypermetropic eye.
16. 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? Draw ray diagram for the correction of this defect.
17. How are we able to see nearby and also the distant objects clearly?
18. 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?
19. How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light? Draw the diagram.
20. Draw a ray diagram showing the dispersion through a prism when a narrow beam of white light is incident on one of its refracting surfaces. Also indicate the order of the colours of the spectrum obtained.
21. Is the position of a star as seen by us its true position? Justify your answer.
22. Why do we see a rainbow in the sky only after rainfall? 23. Why is the colour of the clear sky blue?
24. What is the difference in colours of the Sun observed during sunrise/sunset and noon? Give explanation for each.
LONG ANSWER QUESTIONS
25. Explain the structure and functioning of Human eye. How are we able to see nearby as well as distant objects?
26. When do we consider a person to be myopic or hypermetropic? Explain using diagrams how the defects associated with myopic and hypermetropic eye can be corrected?
27. Explain the refraction of light through a triangular glass prism using a labelled ray diagram. Hence define the angle of deviation.
28. How can we explain the reddish appearance of sun at sunrise or sunset? Why does it not appear red at noon?
29. Explain the phenomenon of dispersion of white light through a glass prism, using suitable ray diagram.
30. How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?
CHAPTER - 12
ELECTRICITY
