# NCERT Optics Class 12 Most Important Questions for Board Exams

## NCERT Class 12 physics Important Questions with Answers

Important 1 Mark ray wave optics Questions for class 12 physics to get good mark in board exams

Optics important Short Questions for Class 12 Physics With Solutions 2021

Important Questions for Class 12 Physics with Answers and Solutions Pdf free download was designed by expert teachers from latest edition of NCERT books to get good marks in board exams. Here we have given Important Questions For Class 12 Physics

NOTE: NCERT Questions for Class 12 Physics Chapter wise questions with answer available for reading or download on this page. Students who are in class 12th or preparing for any exam which is based on Class 12 Physics can refer NCERT Physics Book for their preparation also.

1 .A plane mirror is approaching you at 10 m/sec. You can see your image in it. At what speed will your image approach you ?
(a) 10 cm/sec
(b)5 cm/sec
(c)15 cm/sec
(d) 20 cm/sec

1. A convex mirror is used to form an image of real object. Then tick the wrong statement.
(a) The image lies between pole and the focus.
(b) The image is diminished.
(c) The image is erect.
(d) The image is real.

3.A plane mirror reflecting a ray of incident light is rotated through an angle 6 about an axis o through the point of incidence in the plane of the mirror perpendicular to the plane of incidence then
(a) the reflected ray does not rotate
(b) the reflected ray rotates through an angle
(c) the reflected ray rotates through an angle 20
(d) the incident ray is fixed

1. A worm crawls towards a polished metal ball 24 cm in diameter lying on a table. How far from the surface of the ball is the worm ? When its image appears to be at the centre of the ball ?
(b) 24 cm
(a) 12 cm
(d) 4 cm
(c) 6 cm
5. A man runs towards a mirror at a rate of 6 m/ sec. If we assume the mirror to be at rest, his image will have velocity:
(b)+6 m/sec
(a) +12 m/sec
(d) -12 m/sec
(c)6 m/sec

6.A virtual image larger than the object can be produced by:
(a) concave mirror (b) convex mirror
(d) concave lens
(c) plane mirror

7.The light reflected by a plane mirror may form a real image
(a) if the rays incident on the mirror are converging
(b) if the rays incident on the mirror are diverging
(c) under no circumstances
(d) if the object is placed very close to the miror

8.A ray of light travels from an optically denserto a rarer medium. The critical angle for the two media is c. The maximum possible deviation of the ray will be:
(b)2-
(a) 2c
(d) t 2c
(c) Tt Cc

9.The refractive index of glass is 1.5. What is the speed of light in glass ‘2(speed of light in vacuum is 3 x 10* m/s)
(b) 3x 10 m/sec
(a) 2x 10 m/sec
(c) 2.5 x 10 m/sec
(d) 3.5x 10 m/sec

1. A convex mirror gives images which are
(a) real and inverted
(b) real and erect
(C) virtual and inverted
(d) virtual and erect
2. An object is placed between two plane mirrors inclined at an angle 45°. The number of images seen will be :
(a) 12
(b) 7
(c)4
(d) none of the above
3. A man is approaching a plane mirror at the rate of 3 miles per hour. Then his image approaches him at the rate of:
(a) 3 miles per hour
(b) 6 miles per hour
(c) 1.5 miles per hour
(d) 1 mile per hour
4. Alight bulb is placed between two plane mirrors inclined at an angle of 60. The number of images
formed are

(a) 4
(b) 2
(c) 6
(d) 5
14. The minimum distance between a source and image is possible the screen for which a real with a convex lens is
(a) its focal length
(b) twice the focal length
(c) four times the focal length
(d) square of the focal length
1. If the focal length of the lens is 10 cm the power of lens is:
(b) 0.1 D
(a) 1 D
(d) 10 D
(c) 0.01D

16.When the light travels from glass to air, the. there will be no change in its:
(b) frequency
(a) wavelength
(d) amplitude
(c) velocity

1. Air bubble, in water, will act like:

(a) aconverging lens
(b) a divering lens
(c) ncither a converging nor a diverging lens
(d) none of the above

1. Focal length of a convex lens is 30 cm, when measured in air. When the focal length is measured in water, it is:
(a) greater than 30 cm (b) less than 30 cm
(d) none of the above
(c) equal to 30 cm
2. Light travels through a glass plate of thickness and having refractive index n. If ‘c’ is the velocity sg of the light in vaccum, the time taken by the light to travel this thickness of glass is
(a) t/nc
(b)tnc
(c)nt/c
(d) tc/n
3. A convex lens of focal length 5 cm is in contact with a concave lens of focal length 10 cm. The combined lens is converging lens of focal length 5 cm
(a) conversing lens of focal length 5 cm
(a) converging lens of focal length 10 cm
(C)diverging lens of focal length 10 cm
d) diverging lens of focal length 5 cm
4. The type of aberration present in lens but no mirror is
(b) astigmation
(a) spherical
(d) chromatic
(c) curvature
5. yellow flower if looked through red glass will look like :
(b) blue
(a) black
(c) yellow
(d) red
6. If a red rose is observed in a back ground of white light, it would appear
(a) enish yellow
(b) completely black
(c) red as before
(d) blue

24.when a beam of red light is refracted by a prism the angle of minimum deviation, the angle of emergence
(a)is smaller than the angle of incidence
(b) is equal to the angle of incidence
(c) is ater thar the angle of incidence
(d) plus angle of incidence is equal to zero

25.formation of rainbow is an example of
(c) larisatior of light
(d) dispersion of light
(a)interference of light
(b) diffraction of light

26.The refractive index of glass is minimum of light of which colour ?
(a) red
(b) bluc
(c)yellow
(d) none of the above

27.Angle of prismA and its one surface is silvered. Light rays falling at an angle of incidence 2A on first surface return back through the same path after suffering reflection at second silvered curface. Refractive index of material is:
(a) 2 sinA
(b) 2 cos A
(c) 2 cos A
(d) tan A

1. The splitting of white light into several colour on passing through a glass prism is due to
(a) refraction
(b) reflection
(c) interference
(d) diffraction
2. A thin prism P, of angle of prism 4° and refractive index 1.54 is combined with another thin prism P, of refractive index 1.72 for dispersion without deviation. The angle of prism of P, is
(a) 5.33
(b)4⁰
(d) 2.6
(c) 3
3. The angle of a prism is 5° and its refracting indices for red and violet colours are 1.5 and 1.6 respectively. The angular dispersion produced by the prism is
(b) 0.5°
(a) 7.75°
(d) 0.17
(c) 5
4. Which one of the following phenomena is not explained by Huygen’s construction of wave front?
(b) reflection
(a) refraction
(d) origin of spectra
(c) diffraction
5. gen’s wave theory of light cannot explain:
(b) interference
(a) diffraction
(C) polarization
(d) photoelectric effect
6. If light of low wavelength is used in Young’s double slit experiment then width of the fringge will
(b) increase
(a) decrease e7
(d) no change
(c) not fixed

34.In Young’s double slit experiment on interference the ratio of the intensities of a bright band and a dark band is 16: 1. The ratio of the amplitudes of the interfering waves is:
(a) 16
(b) 5/3
(d)1/ 4
(c) 43s

1. In a wave the path difference corresponding to
phase difference of o is:

(b)π
(a 2
(c)2
2. In Young’s experiment fringe width was found to be 0.4 mm. If whole apparatus is immersed in water of refractive index (u) = 4/3, new fringe width is:
(b) 10.30 mm
(a) 0.25 mm
(d) 0.53 mm
(c) 0.40 mm

37.The fringe width in Young’s double slit experiment increases when:
(a) wavelength increases
(b) distance between the source and screen increases
(c) distance between the slits increases 0
(d) the width of the slit increases

38.In Young’s double slit experiment the source illuminating the slits is changed from blue to violet The width of the fringes

(a) increases
(b) decreases
(c) remains constant
(d) none of the above

1. In Young’s double slit experiment, the central bright fringe can be identified:
(a) as it is narrower than other bright fringes
(b) by using white light instead of monochromatic light
(C) as it has a greater intensity than other brnght fringes
(d) as it is wider than other bright fringes
2. What is the path difference for destructive interference?
(a) nA
(c)(2n+1)
(b)(n+1)
(c)(n+1)¥÷2
3. The power of glass slab is
(b)more
(a) less
(d)infinite.
(c) zero
4. The sign of power of a convex lens is
(b) +ve
(a) -ve
(d) infinite.
(c) zero
5. The sign of power of a concave lens is
(b)+ve
(a) -ve
(d) infinite
(c) zero
6. Twinkling of stars is due to
(b) reflection
(a) refraction
(d) none of these.
(c) dispersion
7. The phenomenon of mirage is due to
(b) reflection
(a) refraction
(d) none of these.
(c) dispersion
8. Diamond dazzles due to
(a) total internal reflection
(b) reflection
(c) refraction
(d) none
9. Optical fiber works on the principle of
(a) reflection
(b) refraction
(c) total internal reflection
(d) none.
10. During sun-rise and sun-set, the colour of sky is
(a) redta
(b) yellow
(c) green
(d) blue.
11. Sky is blue, due to
(a) reflection
(b) refraction
(c) scattering
(d) none of these.
12. For giving colour to the sky in the morning, the sun rays are
(a) diffused
(b) scattered
(c) refracted
(d) reflected