LIGHT

1.   An object of size 1.5 cm is placed at a distance of 30 cm from a concave mirror of focal length 20 cm. Find the position, size and nature of the image formed.
2.   An object of size 1 cm is placed at a distance of 18 cm from a concave mirror of focal length 12 cm. Find the position, size and nature of the image formed.
3. An object 3 cm high produces an image of 4.5 cm when placed at a distance of 20 cm from a concave mirror. Calculate the position size and the nature of the image formed.
4. An object forms 2.5 times magnified real image when placed at a distance of 16 cm from a concave mirror. Calculate the position of image and the focal length of the mirror
5. An object 1.5 cm high placed in front of a concave mirror produces a virtual image 3 cm high. If the object is placed at a distance of 6 cm from the pole of the mirror, calculate the position of the image and the focal length of the mirror.
6. A converging mirror forms three times magnified virtual image when an object is placed at a distance of 8 cm from it. Calculate the position of the image and the focal length of the mirror.
7. An object 5 cm high forms a virtual image 1.25 cm high in front of a convex mirror at a distance of        24 cm. Calculate the position of the image and the focal length of the mirror
8. An object forms virtual image which is 1/8th the size of the object. If the object is placed at a distance of 40 cm from the convex mirror. Calculate the position of the image and the focal length of the mirror
9. An object 5 cm high is placed 20 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed to obtain a sharp image. Also calculate the size of the image formed 
10. The radius of curvature of a convex mirror used in a moving auto mobile is 2 m. A truck is coming from behind at a constant distance of 3.5 m. Calculate the position and the size  of the image relative to the size of the truck. What is the nature of the image 
11. Where should an object be placed from a converging mirror of focal length 20 cm so as to obtain an image of magnification 2
12. Find the position of the object which when placed in front of a convex mirror produces a virtual image which is half the size of the object 
13. An object is placed 20 cm from a convex mirror and its image is formed at 12 cm from the mirror. Find the focal length of the mirror 
14. What is the focal length of the plane mirror? Using mirror formula prove that the image formed by a plane mirror is as far behind the mirror as the object is in front of it 
15. A convex mirror used in a bus has a radius of curvature of 3.5 m, if the driver of the bus locates a car at a distance of 10 m behind the bus, find the position size and nature of the image of the car
16.  A concave mirror of focal length 10 cm produces a real image on its axis 20 cm away from the mirror. Find the position of the object
17. A concave mirror produces a real image of size 3 times that of the object at a distance of 30 cm from the pole of the concave mirror. Find the position of the object
18. How far should an object be from the pole of a concave mirror of focal length 20 cm to form a real image 1/5 th the size of the object
19. A spherical mirror produces a virtual image of an object placed at 10 cm from the pole of the mirror at 30 cm from it. Find the focal length and the nature of the mirror 
20.  An object is placed in front of a concave mirror of focal length 20 cm. The image formed is three times the size of the object, calculate the two possible distances of the object from the mirror
21. When an object is placed at a distance of 60 cm from a convex mirror the magnification is ½ , where should the object be placed to get the magnification of 1/3
22.   An object is placed 18 cm in front of a spherical mirror. If the image is formed at 4 cm to the right of the mirror, calculate the focal length. Is the mirror concave or convex? What is the nature of image
23. The focal length of concave mirror is 10 cm. Where should an object be placed in front of the mirror so that image which is half the size of object is formed 
24. The focal length of concave mirror is 30 cm. Where should an object be placed so that it produces i) real image  ii) virtual image, with magnification 2
25. Find the position of the object placed in front of a concave mirror of focal length 15 cm so that it forms magnified image thrice the size of the object.
26. We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror?
27.  A convex mirror used on a bus has a focal length of 200 cm. If a scooter is located at 400 cm from this mirror, find the position, nature and magnification of the image formed in the mirror.
28.   A 5.0 cm tall 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. By calculation determine (i) the position and (ii) and size of the image formed.
29. An object 5 cm high is placed 20 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed to obtain a sharp image? Calculate the size of the image formed
30. An object 15 cm in length is placed at a distance of 10 cm in front of a convex mirror of focal length 15 cm. Find the position, nature and size of the image formed
31.  A rod of length 10 cm lies along the principal axis of a concave mirror of f= 10 cm in such a way that the end closer to the pole is 20cm away from it. Find the length of image?
32.  An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image.
33. An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.
34. A light of wave length 800 nm in air enters in diamond  with refractive index 2.42 ,calculate the speed , frequency and wavelength of light in diamond if the speed of light in air is 3x10⁸ m/s
35.  A convex lens of focal length 10 cm is placed at a distance of 12 cm from a wall. Calculate the distance from the lens where an object be placed so as to form its distinct real image on the wall.
36.  A convex lens of focal length 40 cm and a concave lens of focal length 50 cm are placed in contact with each other. Calculate : (i) the power of the combination, (ii) focal length of the combination
37.  A point object is placed at a distance of 12 cm from a convex lens on its principal axis. Its image is formed on the other side of the lens at a distance of 18 cm from the lens. Find the focal length of the lens. Is the image magnified? Justify your answer.
38. A convex lens of focal length 20 cm is placed at a distance of 24 cm from the screen. How far from the lens should an object be placed so as to form a real image on the screen? Also find the nature and magnification produced by the lens.
39.   A needle placed 45 cm from a lens forms an image on a screen placed 90 cm on the other side of the lens. Identify the type of lens. Determine its focal length and the power. What is the size of image if, needle is 5 cm in height?
40.  An object is 2 m away from a lens, which forms an erect image one-fourth the size of the object. Determine the focal length of the lens. What type of lens is this?
41.  A concave mirror produces three times enlarged real image of an object placed at 12 cm in front of it. Calculate the radius of curvature of the mirror
42. An object is placed at a distance 100 cm from a lens of power –4 D. Find the position and nature of image so formed.
43. An object is placed at a distance of 20 cm from the optical centre of a convex lens of focal length 30 cm. Find the distance of the image from the lens. What will be the height of the image if the object is 2 cm tall?
44. An object is placed at a distance of 24 cm from the optical centre of a convex lens of focal length 18 cm. Find the distance of the image from the lens. What will be the height of the image if the object is 3.0 cm tall?
45.   A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed
46. An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.
47.  A concave lens has a focal length of 15 cm. At what distance should an object 10 cm long be placed so that it forms an image of 10 cm from the lens? Find the nature and size of the image formed.
48. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed.
49.   An object 3.0 cm high is placed perpendicular to the principal axis of a concave lens of focal length 15.0 cm. The image is formed at a distance of 10.0 cm from the lens. Calculate (i) distance at which the object is placed and (ii) size and nature of the image formed.
50. A convex lens has a focal length of 25 cm. Calculate the distance of the object from the lens if the image is to be formed on the opposite side of the lens at a distance of 75 cm from the lens. What will be the nature of the image?
51. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image as 15 cm from the lens? Also calculate the size of the image formed.
52.  An object when placed in front convex lens forms a real image of 0.5 magnification. If the distance of image from the lens is 24 cm, calculate the focal length of lens
53. A convex lens forms a real image four times magnified at a distance of 6 cm from lens. Calculate the focal length and power of lens
54. A convex lens forms a 2.5 times magnified virtual image when an object is at a distance of 8 cm from the lens, find the image distance  and hence the focal length of the lens
55. An object 1 cm high is placed at a distance of 4 cm from a convex lens of focal length 6 cm. Calculate the position size and the nature of the image formed.
56. How far should screen be placed in front of a convex lens of focal length 10 cm, to obtain a sharp image of an object 3 cm high placed 24 cm from the lens. Also find its size.
57.  A concave lens forms four times diminished and virtual image when an object is placed at a distance of 80 cm from it. Calculate the position of the image and the focal length of the lens
58. A concave lens has a focal length of 15 cm, at what distance should an object be placed from the lens so as to form an image at a distance of 10 cm from it. Also find its magnification
59. The power of the glasses of a person is +0.75 D. What is the nature and the focal length of the lens
60. The power of the thin convex lens is +3.5 D. It is placed in contact with another thin lens so that  the combined power is 1 D. Calculate the power and the focal length of the second lens
61.  Calculate the power and the focal length of a combination of a convex lens and a concave lens of focal length 25 cm and 10 cm respectively
62. The velocity of light in air is 3× 10⁸ ms^–1 and in diamond is 1.2 × 10⁸ ms^–1. Find the refractive index of diamond.
63.  The velocity of light in air is 3x10⁸ m/s and in glass is 2x10⁸ m/s. Find the refractive index of glass with respect to air.
64. The velocity of light in air is 3x10⁸ m/s, calculate  the velocity of light in diamond if the  refractive index of diamond is 2.5
65. A light of wave length 600 nm in air enters in water with refractive index calculate the speed , frequency and wavelength of light in water
66.   Light enters from air to water having refractive index 4/3. What is the speed of light in water? Speed of light in vacuum is 3 × 10⁸ ms^–1.
67. The focal length of the glasses of a short-sighted person is 37.5 cm. Calculate the power of glasses and their nature.
68. Two lenses of power –2.5 D and + 1.5 D are placed in contact. Find the total power of the combination of lenses. Calculate the focal length of this combination
69.  Identify the nature of the mirror and mention two characteristics of the image formed when magnification (m) = + 6.
70. The far point of a myopic eye is 80 cm. What is the nature, power and the focal length of the corrective lens
71.  A person needs a lens of power – 4.5 D for correcting distant vision. For correcting the near vision he needs a lens of power + 2.5 D. What is the focal length these lenses.
72. The near point of a long sighted person is 75 cm. What is the power of lens required to correct this defect. Assume the near point of the eye is 25 cm
73. The near point of a hypermetropic eye is 60 cm. What is the power of the lens required to correct his vision if the near point is 30 cm.
74.    The far point of a myopic person is 40 cm, find the nature, power and the focal length of the corrective lens.( - 0.4 m , - 2.5D )
75.   Near point of a hypermetropic person is 50 cm. What should be the focal length sand the power of the lens if he wants to read a newspaper placed 20 cm away?