CBSE Class 12 Physics Wave Optics MCQs Set D

Question. Diffraction aspect is easier to notice in case of the sound waves then in case of the light waves because sound waves
(a) Have longer wavelength
(b) Shorter wavelength
(c) Longitudinal wave
(d) Transverse waves

Answer: A

Question. What is the relation between refractive index and critical angle for a medium.
(a) n = 1/sin ic
(b) n = sin ic
(c) 1 = n/ sin ic
(d) None of the above

Answer: A

Question. The Sun looks reddish while sunset or sunrise, because.
(a) red colour is highly scattered.
(b) red colour is least scattered.
(c) of refraction of light.
(d) of dispersion of light.

Answer: B

Question. What is the angle made by the ray of light on the wavefront?
(a) 90˚
(b) 0˚
(c) 45˚
(d) None of the above

Answer: A

Question. Which parameter remains unchanged while a ray of light propagates from one medium to another?
(a) velocity
(b) Wave length
(c) frequency
(d) None of the above

Answer: C

Question. According to the above given fig., identify the correct expression for Snell’s law.
(a) n1 sin i = n2 sin r
(b) n2 sin i = n1 sin r
(c) n21 = sin r/ sin i
(d) None of the above

Answer: A

Question. The above given phenomenon cannot be observed on the moon because
(a) total internal reflection could not take place on the moon
(b) there is no atmosphere
(c) Sun is not visible from the moon
(d) None of the above

Answer: B

Question. What is the path difference between the two light waves coming from coherent sources, which produces 3rd maxima.
(a) λ
(b) 2λ
(c) 3λ
(d) 0

Answer: C

Question. What is the correct expression for fringe width(λ).
(a) λd/D
(b) λdD
(c) d/λD
(d) λD/d

Answer: D

Question. Diffraction effects show that light does not travel in straight lines. Under what condition the concepts of ray optics are valid. ( D = distance of screen from the slit).
(a) D < Zf
(b) D = Zf
(c) D > Zf
(d) D << Zf

Answer: D

Question. What is refractive index of a medium(in terms of real and apparent depth).
(a) Real depth/ App depth
(b) App/ Real depth
(c) App X Real depth
(d) Real + App depth

Answer: A

Question. When a ray of light travels from a denser to a rarer medium, it
(a) it bends towards the normal
(b) it travels in a straight line irrespective of angle of incidence.
(c) it bends away from the normal
(d) None of the above

Answer: C

Question. The ratio of the widths of two slits in Young’s double slit experiment is 4 : 1. Evaluate the ratio of intensities at maxima and minima in the interference pattern.
(a) 1:1
(b) 1:4
(c) 3:1
(d) 9:1

Answer: D

Question. What is the principal behind Advance sunrise and delayed sunset.
(a) Reflection.
(b) Refraction.
(c) Dispersion
(d) Total internal reflection.

Answer: B

Question. For how much time the sun is visible apparently after sunset.
(a) Approx. 5 minutes
(b) Approx. 10 minutes
(c) Approx. 2 minutes
(d) None of the above

Answer: C

Question. In a Young’s double slit experiment, the separation between the slits is 0.1 mm, the wavelength of light used is 600 nm and the interference pattern is observed on a screen 1m away. Find the separation between bright fringes.
(a) 6.6 mm
(b) 6.0 mm
(c) 6 m
(d) 60cm

Answer: B

Question. what is the phase diff. between two interfering waves producing 1st dark fringe.
(a) π
(b) 2π
(c) 3π
(d) 4π

Answer: A

Question. In the phenomena of Diffraction of light when the violet light is used in the experiment is used instead of red light then,
(a) Fringe width increases
(b) No change in fridge width
(c) Fringe width decreases
(d) Colour pattern is formed

Answer: C

Question. when 2nd secondary maxima is obtained in case of single slit diffraction pattern, the angular position is given by
(a) λ
(b) λ/2
(c) 3λ/2
(d) 5λ/2

Answer: D

Question. What is refractive index of a medium(in terms of speed of light)
(a) Speed of light in medium/speed of light in vacuum
(b) Speed of light in vacuum/speed of light in medium
(c) Speed of light in medium X speed of light in vacuum
(d) None of the options

Answer: B

Question. In the above diagram, calculate the speed of light in the liquid of unknown refractive index.
(a) 1.2 × 108 m/𝑠
(b) 1.4 × 108 m/𝑠
(c) 1.6 × 108 m/𝑠
(d) 1.8 × 108 m/𝑠

Answer: D