Q.1 What phenomenon explains the spreading of light when it passes through a narrow slit?
Reflection
Refraction
Diffraction
Polarization
Explanation - Diffraction is the bending and spreading of waves when they encounter an obstacle or pass through a narrow aperture.
Correct answer is: Diffraction
Q.2 Two waves of the same frequency interfere and produce alternating bright and dark fringes. What type of interference is this?
Constructive Interference
Destructive Interference
Both
None
Explanation - Bright fringes are due to constructive interference (waves in phase), while dark fringes are due to destructive interference (waves out of phase).
Correct answer is: Both
Q.3 Which experiment demonstrates the interference of light?
Young's Double Slit Experiment
Newton's Rings Experiment
Michelson Interferometer
All of the above
Explanation - Young's experiment, Newton's Rings, and Michelson Interferometer all demonstrate interference effects of light under different conditions.
Correct answer is: All of the above
Q.4 In Young’s double slit experiment, if the slit separation is doubled, what happens to the fringe width?
Doubles
Halves
Remains the same
Quadruples
Explanation - Fringe width β = λD/d, where d is slit separation. Doubling d reduces fringe width by half.
Correct answer is: Halves
Q.5 The central bright fringe in a double slit interference pattern is due to:
Destructive interference
Constructive interference
Diffraction
Polarization
Explanation - The central maximum is formed where the path difference is zero, leading to constructive interference.
Correct answer is: Constructive interference
Q.6 Which of the following is a requirement for observing clear interference fringes?
Coherent sources
Monochromatic light
Stable sources
All of the above
Explanation - Clear interference requires light waves that are coherent, monochromatic, and from stable sources.
Correct answer is: All of the above
Q.7 Newton's rings are observed due to:
Reflection only
Refraction only
Interference of reflected light
Diffraction
Explanation - Newton's rings are formed by the interference of light reflected from the top and bottom surfaces of a thin air film.
Correct answer is: Interference of reflected light
Q.8 In a thin film of thickness t, the condition for constructive interference for reflected light is:
2nt = (m+1/2)λ
2nt = mλ
nt = mλ
nt = (m+1/2)λ
Explanation - For reflected light, a phase change of π occurs at reflection from a denser medium, leading to the condition 2nt = (m+1/2)λ for constructive interference.
Correct answer is: 2nt = (m+1/2)λ
Q.9 Which phenomenon is utilized in anti-reflection coatings on lenses?
Diffraction
Polarization
Interference
Refraction
Explanation - Thin films of specific thickness cause destructive interference of reflected light, reducing reflections from lenses.
Correct answer is: Interference
Q.10 The intensity at a point in interference of two waves is maximum when the phase difference is:
π/2
π
0 or 2π
3π/2
Explanation - Maximum intensity occurs during constructive interference when waves are in phase (phase difference = 0, 2π, ...).
Correct answer is: 0 or 2π
Q.11 Coherent sources are defined as sources that:
Emit light of same color
Emit light of constant phase difference
Have same amplitude
Have same intensity
Explanation - Coherent sources maintain a constant phase difference, necessary for stable interference patterns.
Correct answer is: Emit light of constant phase difference
Q.12 Which type of wave is light considered in wave optics?
Longitudinal
Transverse
Mechanical
Pressure
Explanation - Light is an electromagnetic wave with oscillations perpendicular to the direction of propagation, i.e., transverse.
Correct answer is: Transverse
Q.13 The fringe width in a double slit experiment is directly proportional to:
Slit separation
Wavelength
Both wavelength and distance to screen
Intensity of light
Explanation - Fringe width β = λD/d, directly proportional to wavelength λ and distance D to the screen.
Correct answer is: Both wavelength and distance to screen
Q.14 In interference patterns, dark fringes occur due to:
Constructive interference
Destructive interference
Refraction
Diffraction
Explanation - Destructive interference occurs when waves are out of phase, resulting in cancellation and dark fringes.
Correct answer is: Destructive interference
Q.15 Which type of light is most suitable for observing interference clearly?
White light
Monochromatic light
Polychromatic light
UV light
Explanation - Monochromatic light has a single wavelength, producing stable and clear interference fringes.
Correct answer is: Monochromatic light
Q.16 Michelson interferometer is primarily used to:
Measure wavelength of light
Measure small distances
Study spectral lines
All of the above
Explanation - Michelson interferometer is a precise instrument used for wavelength measurement, small distance detection, and spectral studies.
Correct answer is: All of the above
Q.17 The number of bright fringes per unit length on the screen increases when:
Slit separation increases
Slit separation decreases
Wavelength decreases
Screen distance decreases
Explanation - Fringe width β = λD/d; decreasing d reduces fringe width, increasing the number of fringes per unit length.
Correct answer is: Slit separation decreases
Q.18 In a thin wedge-shaped film, the fringes are due to:
Diffraction
Interference
Polarization
Reflection
Explanation - The varying thickness of the wedge-shaped film causes path difference leading to interference fringes.
Correct answer is: Interference
Q.19 Which of the following affects the spacing of Newton's rings?
Radius of curvature of lens
Wavelength of light
Refractive index of medium
All of the above
Explanation - The radius of Newton's rings depends on lens curvature, light wavelength, and medium’s refractive index.
Correct answer is: All of the above
Q.20 The condition for destructive interference in reflected light from a thin film of thickness t is:
2nt = mλ
2nt = (m+1/2)λ
nt = mλ
nt = (m+1/2)λ
Explanation - For reflected light, if there is one phase change, destructive interference occurs when 2nt = mλ.
Correct answer is: 2nt = mλ
Q.21 Diffraction grating is used to:
Disperse light into spectrum
Increase intensity of light
Reduce interference
Polarize light
Explanation - A diffraction grating separates light into its component wavelengths, forming a spectrum due to interference.
Correct answer is: Disperse light into spectrum
Q.22 The angular width of a diffraction maximum is inversely proportional to:
Wavelength
Slit width
Distance to screen
Number of slits
Explanation - A narrower slit causes greater spreading (diffraction), so angular width is inversely proportional to slit width.
Correct answer is: Slit width
Q.23 The bright and dark rings observed in Newton's rings are due to:
Reflection only
Refraction only
Interference of light
Diffraction only
Explanation - The rings result from constructive and destructive interference of light reflected from thin film surfaces.
Correct answer is: Interference of light
Q.24 If wavelength of light used in a double slit experiment is increased, the fringe width:
Increases
Decreases
Remains same
Becomes zero
Explanation - Fringe width β = λD/d; increasing λ increases fringe spacing.
Correct answer is: Increases