Wave optics mcq questions with answers class 12
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1. According to Huygens' principle, each point on a wave front acts as:
A. A point of reflection
B. A source of sound
C. A source of secondary wavelets
D. A source of primary disturbance
The correct answer is C. A source of secondary wavelets.
Explanation:
Huygens' principle states that each point on a given wave front acts as a source of new disturbances, called secondary wavelets, which spread out in all directions. The surface touching these wavelets forms the new wave front.
Explanation:
Huygens' principle states that each point on a given wave front acts as a source of new disturbances, called secondary wavelets, which spread out in all directions. The surface touching these wavelets forms the new wave front.
2. The phenomenon where light spreads as it passes through a narrow slit is known as:
A. Interference
B. Diffraction
C. Polarization
D. Refraction
The correct answer is B. Diffraction.
Explanation:
Diffraction is the bending and spreading of light waves as they pass through a narrow opening or around obstacles. This phenomenon is observed with narrow slits or small openings.
Explanation:
Diffraction is the bending and spreading of light waves as they pass through a narrow opening or around obstacles. This phenomenon is observed with narrow slits or small openings.
3. In Young's double-slit experiment, the fringe width \( w \) is given by:
A. \( w = \frac{D \lambda}{d} \)
B. \( w = \frac{d \lambda}{D} \)
C. \( w = \frac{D d}{\lambda} \)
D. \( w = \frac{\lambda}{d D} \)
The correct answer is A. \( w = \frac{D \lambda}{d} \).
Explanation:
In Young's double-slit experiment, the fringe width \( w \) is calculated as the ratio of the product of the distance between the slits and the screen \( D \) and the wavelength \( \lambda \), to the slit separation \( d \).
Explanation:
In Young's double-slit experiment, the fringe width \( w \) is calculated as the ratio of the product of the distance between the slits and the screen \( D \) and the wavelength \( \lambda \), to the slit separation \( d \).
4. The condition for constructive interference in a two-slit experiment is that the path difference should be:
A. A half multiple of \( \lambda \)
B. A quarter multiple of \( \lambda \)
C. An integer multiple of \( \lambda \)
D. Zero
The correct answer is C. An integer multiple of \( \lambda \).
Explanation:
Constructive interference occurs when the path difference between the waves from two sources is an integer multiple of the wavelength \( \lambda \), leading to a bright fringe.
Explanation:
Constructive interference occurs when the path difference between the waves from two sources is an integer multiple of the wavelength \( \lambda \), leading to a bright fringe.
5. In single-slit diffraction, the angular width of the central maximum is approximately:
A. \( \frac{\lambda}{D} \)
B. \( \frac{d}{2 \lambda} \)
C. \( \frac{2 \lambda}{d} \)
D. \( \frac{\lambda}{d} \)
The correct answer is C. \( \frac{2 \lambda}{d} \).
Explanation:
For single-slit diffraction, the angular width of the central maximum is given by \( \frac{2 \lambda}{d} \), where \( \lambda \) is the wavelength and \( d \) is the slit width.
Explanation:
For single-slit diffraction, the angular width of the central maximum is given by \( \frac{2 \lambda}{d} \), where \( \lambda \) is the wavelength and \( d \) is the slit width.
6. The phase difference required for destructive interference in a two-slit experiment is:
A. \( 0 \)
B. \( \pi \)
C. \( 2 \pi \)
D. \( \pi/2 \)
The correct answer is B. \( \pi \).
Explanation:
Destructive interference occurs when the phase difference between two waves is \( \pi \) radians (180 degrees), resulting in cancellation of the wave amplitudes.
Explanation:
Destructive interference occurs when the phase difference between two waves is \( \pi \) radians (180 degrees), resulting in cancellation of the wave amplitudes.
7. The Doppler effect in light is observed as a shift in:
A. Amplitude
B. Speed
C. Frequency
D. Phase
The correct answer is C. Frequency.
Explanation:
The Doppler effect in light refers to a change in the observed frequency when there is relative motion between the light source and the observer.
Explanation:
The Doppler effect in light refers to a change in the observed frequency when there is relative motion between the light source and the observer.
8. The angular position of the first minimum in a single-slit diffraction pattern is given by:
A. \( \sin \theta = \frac{\lambda}{d} \)
B. \( \cos \theta = \frac{d}{\lambda} \)
C. \( \tan \theta = \frac{d}{\lambda} \)
D. \( \sin \theta = \frac{2 \lambda}{d} \)
The correct answer is A. \( \sin \theta = \frac{\lambda}{d} \).
Explanation:
For single-slit diffraction, the first minimum occurs when \( d \sin \theta = \lambda \), where \( d \) is the slit width and \( \lambda \) is the wavelength.
Explanation:
For single-slit diffraction, the first minimum occurs when \( d \sin \theta = \lambda \), where \( d \) is the slit width and \( \lambda \) is the wavelength.
9. Brewster's angle is defined as the angle of incidence at which:
A. The reflected light is partially polarized
B. The reflected and refracted rays are perpendicular
C. The incident light is completely absorbed
D. The refracted light is completely polarized
The correct answer is B. The reflected and refracted rays are perpendicular.
Explanation:
Brewster's angle is the angle of incidence at which the reflected and refracted rays are at 90 degrees to each other, and the reflected light is fully polarized.
Explanation:
Brewster's angle is the angle of incidence at which the reflected and refracted rays are at 90 degrees to each other, and the reflected light is fully polarized.
10. The intensity of light after passing through a polarizer is given by:
A. \( I = I_0 \sin \theta \)
B. \( I = I_0 \cos^2 \theta \)
C. \( I = I_0 \cos \theta \)
D. \( I = I_0 \tan^2 \theta \)
The correct answer is B. \( I = I_0 \cos^2 \theta \).
Explanation:
After passing through a polarizer, the intensity \( I \) of light is given by Malus' law, \( I = I_0 \cos^2 \theta \), where \( I_0 \) is the initial intensity and \( \theta \) is the angle between the light's initial polarization direction and the polarizer's axis.
Explanation:
After passing through a polarizer, the intensity \( I \) of light is given by Malus' law, \( I = I_0 \cos^2 \theta \), where \( I_0 \) is the initial intensity and \( \theta \) is the angle between the light's initial polarization direction and the polarizer's axis.
11. The condition for the minima on either side of the central maximum in single-slit diffraction is given by:
A. \( d \sin \theta = n \lambda \)
B. \( d \cos \theta = n \lambda \)
C. \( \sin \theta = \frac{\lambda}{d} \)
D. \( d = n \lambda \sin \theta \)
The correct answer is A. \( d \sin \theta = n \lambda \).
Explanation:
In single-slit diffraction, minima occur when the path difference between waves from opposite edges of the slit is an integer multiple of the wavelength, \( d \sin \theta = n \lambda \), where \( n \) is an integer.
Explanation:
In single-slit diffraction, minima occur when the path difference between waves from opposite edges of the slit is an integer multiple of the wavelength, \( d \sin \theta = n \lambda \), where \( n \) is an integer.
12. The width of the central maximum in a single-slit diffraction pattern is:
A. \( \frac{\lambda}{d} \)
B. \( \frac{d}{\lambda} \)
C. \( \frac{2 D \lambda}{d} \)
D. \( \frac{\lambda D}{2 d} \)
The correct answer is C. \( \frac{2 D \lambda}{d} \).
Explanation:
The width of the central maximum in a single-slit diffraction pattern is \( \frac{2 D \lambda}{d} \), where \( D \) is the distance from the slit to the screen, \( \lambda \) is the wavelength, and \( d \) is the slit width.
Explanation:
The width of the central maximum in a single-slit diffraction pattern is \( \frac{2 D \lambda}{d} \), where \( D \) is the distance from the slit to the screen, \( \lambda \) is the wavelength, and \( d \) is the slit width.
13. In a two-slit interference experiment, the separation between two bright fringes is:
A. \( \frac{\lambda}{d} \)
B. \( \frac{d}{D} \)
C. \( \frac{D \lambda}{d} \)
D. \( \frac{\lambda d}{D} \)
The correct answer is C. \( \frac{D \lambda}{d} \).
Explanation:
The separation between adjacent bright fringes (fringe width) in a double-slit interference experiment is \( \frac{D \lambda}{d} \), where \( D \) is the distance to the screen, \( \lambda \) is the wavelength, and \( d \) is the distance between slits.
Explanation:
The separation between adjacent bright fringes (fringe width) in a double-slit interference experiment is \( \frac{D \lambda}{d} \), where \( D \) is the distance to the screen, \( \lambda \) is the wavelength, and \( d \) is the distance between slits.
14. When light is polarized by reflection, the reflected and refracted light rays are:
A. Parallel
B. At an angle of 45 degrees
C. Perpendicular
D. In phase
The correct answer is C. Perpendicular.
Explanation:
According to Brewster's law, at the polarizing angle, the reflected and refracted rays are perpendicular to each other.
Explanation:
According to Brewster's law, at the polarizing angle, the reflected and refracted rays are perpendicular to each other.
15. In polarization by scattering, the scattered light is:
A. Partially polarized
B. Fully polarized
C. Unpolarized
D. Dispersed only
The correct answer is A. Partially polarized.
Explanation:
When light is scattered by particles comparable in size to its wavelength, it becomes partially polarized, with the degree of polarization depending on the scattering angle.
Explanation:
When light is scattered by particles comparable in size to its wavelength, it becomes partially polarized, with the degree of polarization depending on the scattering angle.
16. In Young's double-slit experiment, the condition for constructive interference at a point on the screen is:
A. The path difference is \( (2n + 1) \frac{\lambda}{2} \)
B. The path difference is \( n \lambda \)
C. The path difference is zero
D. The phase difference is \( \pi \)
The correct answer is B. The path difference is \( n \lambda \).
Explanation:
Constructive interference occurs when the path difference between two waves is an integer multiple of the wavelength, \( n \lambda \), leading to bright fringes.
Explanation:
Constructive interference occurs when the path difference between two waves is an integer multiple of the wavelength, \( n \lambda \), leading to bright fringes.
17. The relationship between the phase difference \( \Delta \phi \) and path difference \( \Delta x \) in a wave is:
A. \( \Delta \phi = \Delta x \lambda \)
B. \( \Delta \phi = \frac{2 \pi \Delta x}{\lambda} \)
C. \( \Delta \phi = \frac{\Delta x}{\lambda} \)
D. \( \Delta \phi = 2 \pi \Delta x \lambda \)
The correct answer is B. \( \Delta \phi = \frac{2 \pi \Delta x}{\lambda} \).
Explanation:
The phase difference \( \Delta \phi \) corresponding to a path difference \( \Delta x \) is given by \( \Delta \phi = \frac{2 \pi \Delta x}{\lambda} \), where \( \lambda \) is the wavelength.
Explanation:
The phase difference \( \Delta \phi \) corresponding to a path difference \( \Delta x \) is given by \( \Delta \phi = \frac{2 \pi \Delta x}{\lambda} \), where \( \lambda \) is the wavelength.
18. Which of the following statements is true about coherent sources?
A. They must have different frequencies
B. They must have random phase differences
C. They have a stable phase difference
D. They do not produce interference patterns
The correct answer is C. They have a stable phase difference.
Explanation:
Coherent sources are those that have the same frequency and a constant phase difference, enabling stable interference patterns.
Explanation:
Coherent sources are those that have the same frequency and a constant phase difference, enabling stable interference patterns.
19. The intensity of light passing through two crossed polaroids is:
A. Half of the initial intensity
B. The same as the initial intensity
C. Zero
D. Double the initial intensity
The correct answer is C. Zero.
Explanation:
When two polaroids are crossed (placed at 90° to each other), no light passes through, resulting in zero intensity.
Explanation:
When two polaroids are crossed (placed at 90° to each other), no light passes through, resulting in zero intensity.
20. In Young's double-slit experiment, if the distance between the slits is doubled, the fringe width will:
A. Double
B. Remain the same
C. Halve
D. Quadruple
The correct answer is C. Halve.
Explanation:
The fringe width \( w \) in Young's double-slit experiment is given by \( w = \frac{D \lambda}{d} \). If the distance between the slits \( d \) is doubled, the fringe width \( w \) will be halved.
Explanation:
The fringe width \( w \) in Young's double-slit experiment is given by \( w = \frac{D \lambda}{d} \). If the distance between the slits \( d \) is doubled, the fringe width \( w \) will be halved.
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