Q.1 Which phenomenon is responsible for the formation of a rainbow?
Refraction and total internal reflection
Diffraction
Polarization
Interference
Explanation - Rainbows are formed due to refraction of light as it enters and leaves water droplets, along with internal reflection inside the droplet.
Correct answer is: Refraction and total internal reflection
Q.2 The focal length of a convex lens is 20 cm. Its power is:
2.0 D
4.0 D
5.0 D
0.5 D
Explanation - Power (in dioptres) = 100 / focal length (in cm). So, P = 100/20 = 5 D.
Correct answer is: 5.0 D
Q.3 The critical angle for a medium is 30°. The refractive index of the medium with respect to air is:
2.0
1.73
1.5
1.33
Explanation - n = 1/sin(C). For C = 30°, n = 1/sin(30°) = 1/0.5 = 2.0.
Correct answer is: 2.0
Q.4 Which of the following colors is deviated most by a prism?
Red
Green
Blue
Violet
Explanation - Deviation increases with decreasing wavelength. Violet has the shortest wavelength among visible light.
Correct answer is: Violet
Q.5 In Young’s double slit experiment, the fringe width increases if:
Distance between slits increases
Wavelength decreases
Screen distance decreases
Wavelength increases
Explanation - Fringe width β = λD/d. Increasing λ increases β.
Correct answer is: Wavelength increases
Q.6 If the speed of light in a medium is 2 × 10^8 m/s, the refractive index of the medium is:
1.5
2.0
1.33
0.67
Explanation - Refractive index n = c/v = 3×10^8 / 2×10^8 = 1.5.
Correct answer is: 1.5
Q.7 Light waves are:
Longitudinal
Transverse
Mechanical
Sound-like
Explanation - Light consists of oscillating electric and magnetic fields perpendicular to the direction of propagation.
Correct answer is: Transverse
Q.8 Which phenomenon shows that light has wave nature?
Reflection
Refraction
Interference
Photoelectric effect
Explanation - Interference occurs due to superposition of waves, proving light’s wave nature.
Correct answer is: Interference
Q.9 For a plane mirror, the image formed is:
Real and erect
Virtual and erect
Real and inverted
Virtual and inverted
Explanation - A plane mirror always forms a virtual, upright image of the same size behind the mirror.
Correct answer is: Virtual and erect
Q.10 The angular resolution of a telescope depends upon:
Wavelength of light
Refractive index
Mirror thickness
Lens material
Explanation - According to Rayleigh’s criterion, angular resolution ∝ λ/D, where λ is wavelength.
Correct answer is: Wavelength of light
Q.11 Which of the following phenomena cannot be explained by wave theory of light?
Interference
Diffraction
Photoelectric effect
Polarization
Explanation - Photoelectric effect requires particle nature of light, explained by photons.
Correct answer is: Photoelectric effect
Q.12 The sky appears blue due to:
Reflection
Dispersion
Rayleigh scattering
Refraction
Explanation - Shorter wavelengths (blue) scatter more than longer ones, making the sky appear blue.
Correct answer is: Rayleigh scattering
Q.13 Which lens is used to correct myopia?
Convex lens
Concave lens
Cylindrical lens
Bifocal lens
Explanation - Myopia (short-sightedness) is corrected using a diverging (concave) lens.
Correct answer is: Concave lens
Q.14 The speed of light is maximum in:
Glass
Diamond
Water
Vacuum
Explanation - Light travels fastest in vacuum where refractive index is 1.
Correct answer is: Vacuum
Q.15 The phenomenon of mirage is due to:
Reflection
Refraction and total internal reflection
Interference
Diffraction
Explanation - Mirages occur due to refraction in layers of hot air and total internal reflection.
Correct answer is: Refraction and total internal reflection
Q.16 Polarization of light can be obtained by:
Prisms
Filters
Reflection
All of the above
Explanation - Polarization can be achieved using Polaroid filters, prisms (Nicol prism), and reflection at Brewster’s angle.
Correct answer is: All of the above
Q.17 Which of the following quantities changes when light enters a medium?
Frequency
Wavelength
Color
Photon energy
Explanation - Frequency remains constant; wavelength changes to keep speed = frequency × wavelength.
Correct answer is: Wavelength
Q.18 When white light passes through a prism, the color deviated least is:
Red
Violet
Blue
Green
Explanation - Red has the longest wavelength and is deviated least by the prism.
Correct answer is: Red
Q.19 The phenomenon of diffraction is more pronounced when:
Wavelength is small
Wavelength is comparable to slit size
Slit is very wide
Slit is opaque
Explanation - Diffraction effects are significant when aperture size is of the order of wavelength.
Correct answer is: Wavelength is comparable to slit size
Q.20 If the magnification of a mirror is +1, the mirror is:
Plane mirror
Concave mirror only
Convex mirror only
Any mirror
Explanation - Plane mirror always produces magnification +1 (virtual and erect image).
Correct answer is: Plane mirror
Q.21 What is the principle of optical fibers?
Reflection
Refraction
Total internal reflection
Diffraction
Explanation - Optical fibers work on total internal reflection of light inside a dielectric medium.
Correct answer is: Total internal reflection
Q.22 Which of the following is a monochromatic source of light?
Sunlight
Mercury lamp
Laser
Bulb filament
Explanation - Laser produces light of a single wavelength (monochromatic).
Correct answer is: Laser
Q.23 Brewster’s angle is related to:
Polarization
Interference
Diffraction
Refraction
Explanation - At Brewster’s angle, reflected light is completely plane polarized.
Correct answer is: Polarization
Q.24 In double slit experiment, if slit separation is doubled, fringe width becomes:
Half
Double
Unchanged
Four times
Explanation - Fringe width β = λD/d. Increasing d reduces β.
Correct answer is: Half
Q.25 Which property of light is utilized in sunglasses?
Diffraction
Polarization
Refraction
Dispersion
Explanation - Polaroid sunglasses reduce glare by blocking polarized light.
Correct answer is: Polarization