LIGHT
CLASS: X
1. The path along which light travels in a homogenous medium is called the :
(A) beam of light (B) ray of light (C) pencil of light (D) none of these
2. A thin layer of water is transparent but a very thick layer of water is :
(A) translucent (B) opaque (C) most transparent (D) none of these
3. Air is not visible because it _
(A) is nearly a perfectly transparent substance
(B) neither absorbs nor reflects light
(C) transmits whole of light
(D) all the above are correct
4. According to laws of reflection of light :
(A) Angle of incidence is equal to the angle of reflection
(B) Angle of incidence is less than the angle or reflection
(C) Angle of incidence is greater than the angle of reflection
(D) None of these
5. A swimming pool appears to be 2m deep. It actual depth is ( refractive index for water = 1.33)-
(A) 2.66 m (B) 2m (C) 2.34 m (D) 2.54 m
6 A ray of light is incident on a plane mirror at an angle x and the angle between the incident and reflected rays is 65, what is the value of x :
(A) 32.5 (B) 35 (C) 45 (D) None of these
7. When a ray of light enters a transparent medium it undergoes change is :
(A) Frequency only (B) Wavelength only (C) Wavelength and velocity both (D) Velocity and frequency both
8. The focal length of a concave mirror is f m and the distance from the object to the principal focus is a m. The magnitude of magnification obtained will be-
(A) (f + a)/f (B) f/a (C) f / a (D) f2/a2
9. The magnification of an object placed 10 cm from a convex mirror of radius of curvature 20 cm will be.
(A) 0.2 (B) 0.5 (C) 1 (D) infinity
10. The image formed by a concave mirror is observed to be virtual, erect and larger than the object. the position of the object should be-
(A) between the focus and the centre of curvature.
(B) at the centre of curvature
(C) beyond the centre of curvature
(D) between the pole of the mirror and the focus
11. The magnification produces by a concave mirror-
(A) is always more the one
(B) is always less than one
(C) is always equal to one
(D) may be less than or greater than one
12. The image formed by a concave mirror is real, inverted and of the same size as that of the object. The position of the object should be :
(A) Beyond C (B) Between C and F (C) At C (D) At F
13. A boy is standing in front of a place mirror at a distance of 3 m from it. What is the distance between the boy and his image ?
(A) 3 m (B) 4.5 m (C) 6 m (D) none of these
14. Refractive index of glass with respect to air is 1.5 and refractive index of water with respect to air is 3/4 What will be the refractive index of glass w.r.t water ?
(A) 1 (B) 1.5 (C) 1.125 (D) -10
15. The refractive index of a medium depends upon -
(A) Nature of material of the medium
(B) Optical density of the medium
(C) Wavelength of light
(D) All of these
16. A ray of light in incident normally on a rectangular piece of glass. The value of angle of refraction will be-
(A) 1800 (B) 900 (C) 450 (D) 00
17. A fish looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4/3 and the fish is 12 cm below the surface, the radius of the circle is -
(A) 12 × 3 × 5 cm (B) 12 × 3 × 7 cm (C) 12 × 5 / 2 cm (D) None of these
18. The speed of light is vacuum is 3.0 ×108 m/s. If the refractive index of a transparent liquid is 4/3, then the speed of light in the liquid is -
(A) 2.25 × 108 m/s (B) 3 × 108 m/s (C) 4 × 108 m/s (D) 4.33 × 108 m/s
19. 1. To get a real and inverted image of the same size as that the object should be placed in front of the convex lens at:
(A) F (B) 2F C) between F and 2F (D) away from 2F, where F is focal length
20. A spherical mirror and a spherical lens have each focal length of - 10cm. The mirror and lens are :
(A) both convex (B) both concave (C) mirror is convex and lens is concave (D) mirror is concave and lens is convex
21. The power of lens having focal length 50 cm is :
(A) 1/2 D (B) 2D (C) 3D (D) 0.2 D
22. The focal length of a lens of power - 2.0 D is :
(A) -2.0 m (B) 0.2 m (C) 0.5 m (D) 0.5 m
23. Two lenses of +5D and -5D are placed in chose contact. The focal length of the combination is :
(A) Zero (B) infinity (C) Zero or infinity (D) None of these
24 A student needs a lens of power -2.0 dioptre to correct his distant vision. The focal length of the given lens is :
(A) + 50 cm (B) -50 cm (C) 10 cm (D) -10 cm
25. Focal length of coloured goggles (without number) is :
(A) zero (B) infinity (C) between zero & infinity (D) None of these
26. Where should an object be placed so that a real and inverted image of very large size is obtained, using a convex lens ?
(A) At the focus (B) At 2F (C) Between F & 2F (D) Beyond 2F
27. A convex lens is :
(A) Thicker at the middle, thinner at the edges
(B) Diverging
(C) Thicker at the edges thinner in the middle
(D) Of uniform thickness everywhere
28. A glass rod of refractive index 1.42 is immersed in kerosene. The refractive index of kerosene is 1.42. Then the rod will :
(A) appear bent (B) appear raised above the liquid
(C) become invisible (D) none of the above
29. The power of a lens whose focal length is 25 cm is :
(A) 4 Dioptre (B) 25 Dioptre (C) 0.04 Dioptre (D) 2.5 Dioptre
30. A thin lens is made with a material having refractive index n = 1.5. Both the side are convex. It is dipped in water ( n = 1.33), it will be have like :
(A) a convergent lens (B) a divergent lens
(C) a rectangular slab (D) a prism
31. Choose the correct option :
(A) If the final rays are converging, we have a real image.
(B) If the incident rays are converging, we have a real image.
(C) If the image is virtual, the corresponding object is called a virtual object.
(D) The image of a virtual object is called a virtual image.
32. A convex lens forms a real image of a point object placed on its principal axis. If the upper half on the lens is painted black :
(A) the image will be shifted backward
(B) the image will not be shifted
(C) the intensity of the image will decrease
(D) both (B) & (C)
33. The minimum distance between an object and its real image formed by a convex lens of focal length ƒ is :
(A) ƒ (B) 2ƒ (C) 3ƒ` (D) 4ƒ
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