Ray Optics MCQ Questions with Answers Class 12 Physics
Q.- A small plane mirror is placed at the centre of a spherical screen of radius R. A beam of light is falling on the mirror.If the mirror makes n revolutions per second, the speed of light on the screen after reflection from the mirror will be
(a) 4 πnR
(b) 2 πnR
(c) nR/2π
(d) nR/4π
Ans-(a)
Q.- Which of the following is not true about the image formed
by covex mirror?
(a) It is erect
(b) It is virtual
(c) It is diminished
(d) It lies beyond focus
Ans-(d)
Q.- For a real object, a convex mirror always forms an image which is
(a) real and inverted
(b) virtual and inverted
(c) virtual and erect
(d) real and magnified
Ans-(c)
Q.- The image of a bright object is brought on the screen with a concave mirror. If upper half of mirror is covered, what is the effect on the image?
(a) its size is halved
(b) brightness is reduced
(c) image changes position
(d) image disappears
Ans-(b)
Q.- A convex mirror is used to form an image of a real object.Then tick the wrong statement
(a) the image lies between the pole and focus
(b) the image is diminished in size
(c) the image is erect
(d) the image is real
Ans-(d)
Q.- A concave mirror is used to form an image of the sun on a white screen. If the lower half on the mirror were covered with an opaque card, the effect on the image on the screen would be
(a) to make the image less bright than before
(b) to make the lower half of the image disappear
(c) to prevent image from being focussed
(d) none of these
Ans-(a)
Q.- The image formed by a convex mirror of focal length 30 cm is one quarter of the size of object. The distance of object form the mirror is
(a) 30 cm
(b) 120 cm
(c) 90 cm
(d) 60 cm
Ans-(c)
Q.- A convex mirror has a focal length f. A real object is placed at a distance f in front of it from the pole, produces an image at
(a) infinity
(b) f
(c) f/2
(d) 2 f
Ans-(c)
Q.- A concave mirror of focal length f produces an image n times the size of the object. If the image is real then the distance of the object from the mirror, is
(a) (n – 1) f
(b) {(n – 1)/n} f
(c) {(n + 1)/n} f
(d) (n + 1) f
Ans-(c)
Q.- A convex mirror of focal length f produces an image(1/n)th of the size of the object. The distance of the object from the mirror is
(a) nf
(b) f/n
(c) (n + 1)/f
(d) (n – 1) f
Ans-(d)
Q.- The refractive index of water with respect to air is 4/3 and the refractive index of glass with respect to air is 3/2. The refractive index of water with respect to glass is
(a) 9/8
(b) 8/9
(c) 1/2
(d) 2
Ans-(b)
Q.- Air has refractive index 1.0003. The thickness of air column, which will have one more wavelength of yellow light (6000 Å) than in same thickness of vacuum, is
(a) 2 mm
(b) 2 cm
(c) 2 m
(d) 2 km
Ans-(a)
Q.- A glass slab of thickness 8 cm contain, the same number of waves as 10 cm of water when both are traversed by the same monochromic light. If the refractive index of water is 4/3, the refractive index of glass is
(a) 5/3
(b) 5/4
(c) 16/15
(d) 3/2
Ans-(a)
Q.- A beam of monochromatic blue light of wavelength 420 nm in air travels in water (μ = 4/3). Its wavelength in water will be
(a) 280 nm
(b) 560 nm
(c) 315 nm
(d) 400 nm
Ans-(c)
Q.- If velocity of light in a certain medium is 1.5 × 108 m/s, μ for the medium would be
(a) 2
(b) 4
(c) 2.5
(d) 3
Ans-(a)
Q.- The wavelength of sodium light is 589 nm in air. What will be the wavelength of sodium light it it travels in glass of refractive index 1.5 ?
(a) 589 nm
(b) 589 × 1.5 nm
(c) (589/1.5) nm
(d) none of these
Ans-(c)
Q.- Light travels with a speed of 2 × 108 m/s in crown glass of refractive index 1.5. What is the speed of light in dense glass of refractive index 1.8 ?
(a) 1.33 × 108 m/s
(b) 1.67 × 108 m/s
(c) 2.0 × 108 m/s
(d) 3.0 × 108 m/s
Ans-(b)
Q.- If the refractive index of water is 4/3 and that of glass slab is 5/3, then the critical angle of incidence for which a light tending to go from glass to water is
(a) sin–1 3/4
(b) sin–1 3/5
(c) sin–1 2/3
(d) sin–1 4/5
Ans-(d)
Q.- A ray of light enters from a denser medium into rarer medium. The speed of light in the rarer medium is twice that in denser medium. what is the critical angle for total internal reflection to take palce
(a) 60°
(b) 45°
(c) 30°
(d) none of above
Ans-(c)
Q.- The refractive index of water is 4/3 and that of glass is 5/3.What will be the critical angle for the ray of light entering water from the glass
(a) sin–1 (4/5)
(b) sin–1 (5/4)
(c) sin–1 (1/2)
(d) sin–1 (2/1)
Ans-(a)
Q.- A vessel is half filled with a liquid of refractive index μ. The other half of the vessel is filled with an immiscibel liquid of refractive index 1.5 μ. The apparant depth of the vessel is 50% of the actual depth. Then μ is
(a) 1.4
(b) 1.5
(c) 1.6
(d) 1.67
Ans-(d)
Q.- An air bubble in glass slab (μ = 1.5) from one side is 6 cm and from other side is 4 cm. The thickness of glass slab is
(a) 10 cm
(b) 6.67 cm
(c) 15 cm
(d) none of these
Ans-(c)
Q.- If in a planoconvex lens, radius of curvature of convex surface is 10 cm and the focal length of the lens is 30 cm, the refractive index of the material of the lens will be
(a) 1.5
(b) 1.66
(c) 1.33
(d) 3
Ans-(c)
Q.- A double convex lens of focal length 6 cm is made of glass of refractive index 1.5. The radius of curvature of one surface is double that of other surface. The value of large radius of curvature is
(a) 6 cm
(b) 4.5 cm
(c) 9 cm
(d) 4 cm
Ans-(c)
Q.- A lens behaves as a converging lens in air and a diverging lens in water. The refractive index of the material is
(a) equal to unity
(b) equal to 1.33
(c) between unity and 1.33
(d) greater than 1.33
Ans-(c)
Q.- A double convex lens made of material of refractive index 1.5 and having a focal length of 10 cm is immersed in a liquid of refractive index 3.0. The lens will behave as
(a) converging lens of focal length 10 cm
(b) diverging lens of focal length 10 cm
(c) convering lens of focal length 10/3 cm
(d) converging lens of focal length 30 cm
Ans-(b)
Q.- A convergent lens of focal length 20 cm and made of a material with refractive index 1.1 is immersed in water. The lens will behave as a
(a) converging lens of focal length 20 cm
(b) converging lens of focal length less than 20 cm
(c) converging lens of focal length more than 20 cm
(d) divergent lens.
Ans-(d)
Q.- A double convex air bubble in water will behave as
(a) convergent lens
(b) divergent lens
(c) plane glass slab
(d) concave mirror
Ans-(b)
Q.- A lens with power + P is immersed in water. Its power
(a) increases
(b) decreases
(c) remains unchanged
(d) increases for red colour, decreases for blue
Ans-(b)
Q.- Magnification produced by a concave lens cannot be
(a) more than one
(b) equal to one
(c) less than one
(d) equal to or less than one
Ans-(a,b)
Q.- A convex lens of focal length f is put in contact with a concave lens of same focal length. The focal length of combination is
(a) zero
(b) 2f
(c) f
(d) infinity
Ans-(d)
Q.- Two thin lenses of focal lengths 20 cm and 25 cm are placed in contact. The power of the combination is
(a) 0.5 D
(b) 9 D
(c) 5 D
(d) 4.5 D
Ans-(b)
Q.- A concave and convex lens have same focal length of 20 cm and are put in contact. The combination is used to view an object of 5 cm length kept at 20 cm from the lens combination. As compared to object, the image will be
(a) magnified and inverted
(b) diminished and erect
(c) of same size and erect
(d) of same size and inverted
Ans-(c)
Q.- For a normal eye, the least distance of distinct vision is nearly
(a) 10 cm
(b) 25 cm
(c) 50 cm
(d) 100 cm
Ans-(b)
Q.- In a simple microscope, the distance of object from the lens should be
(a) more than the focal length of lens
(b) less than the focal length of lens
(c) more than twice the focal length
(d) more than focal length but less than twice the focal length
Ans-(b)
Q.- An astronomical telescope essentially consists of
(a) two concave lenses
(b) two convex lenses
(c) one concave and one convex lens
(d) two planoconcave
Ans-(b)
Q.- The resolving power of a telescope can be increased by
(a) increasing the focal length of objective
(b) increasing the aperture and diameter of objective
(c) decreasing the focal length of objective
(d) decreasing the aperture diameter of objective
Ans-(b)
Q.- For the normal setting of a telescope
(a) only the object is at infinity.
(b) only the final image is at infinity.
(c) both the object and the final image are at infinity.
(d) neither the object nor the final image has to be at infinity
Ans-(c)
Q.- In a reflecting telescope, the focal length of the eyepiece is 5 cm. What should be the radius of curvature of the objective mirror to have magnifying power of 40 ?
(a) 1m
(b) 2m
(c) 4m
(d) 8 m
Ans-(c)
Q.- The objective of a telescope has focal length 120 cm and diameter 5 cm. The focal length of eyepiece is 2 cm. The magnifying power for an object at infinity is
(a) 24
(b) 60
(c) 12
(d) 300
Ans-(b)
Q.- The powers of the lenses of a telescope are 0.5 and 20 dioptres. Its magnifying power is
(a) 50
(b) 10
(c) 100
(d) 40
Ans-(d)
Q.- The final image formed by an astronomical telescope is
(a) virtual and upright
(b) virtual and inverted
(c) real and upright
(d) real and inverted
Ans-(b)
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