Wave Optics MCQs (Interference, Diffraction, Polarisation)
Wave Optics MCQs
Class: CBSE Class 12
Subject: Physics
Section: Optics
Topic: Interference, Diffraction & Polarisation
Based on: CBSE Board Examination Pattern (NCERT)
Instructions: These Multiple Choice Questions (MCQs) are designed strictly as per the NCERT syllabus, making them ideal for CBSE Class 12 Board Examination preparation.
1. In Young’s Double Slit Experiment, the fringe width depends on:
Answer: D
Fringe width β = λD/d. It depends on wavelength (λ), screen distance (D), and slit separation (d).
Fringe width β = λD/d. It depends on wavelength (λ), screen distance (D), and slit separation (d).
2. Interference is a result of:
Answer: B
Interference occurs due to superposition of coherent light waves producing maxima and minima.
Interference occurs due to superposition of coherent light waves producing maxima and minima.
3. Condition for constructive interference:
Answer: A
Constructive interference occurs when path difference equals integral multiples of wavelength.
Constructive interference occurs when path difference equals integral multiples of wavelength.
4. Diffraction occurs when light passes through:
Answer: C
Diffraction is significant when aperture size is comparable to wavelength.
Diffraction is significant when aperture size is comparable to wavelength.
5. Central maximum in diffraction pattern is:
Answer: B
Central maximum is brightest and twice the width of secondary maxima.
Central maximum is brightest and twice the width of secondary maxima.
6. Polarisation proves that light is:
Answer: B
Only transverse waves can be polarised, proving transverse nature of light.
Only transverse waves can be polarised, proving transverse nature of light.
7. Unit of fringe width is:
Answer: A
Fringe width is a length measurement, so SI unit is metre.
Fringe width is a length measurement, so SI unit is metre.
8. Coherent sources have same:
Answer: B
Coherent sources maintain constant phase difference and same frequency.
Coherent sources maintain constant phase difference and same frequency.
9. Diffraction pattern intensity decreases because:
Answer: B
Light spreads into wider region reducing intensity of successive maxima.
Light spreads into wider region reducing intensity of successive maxima.
10. Brewster’s law relates:
Answer: A
μ = tan iₚ, where iₚ is polarising angle.
μ = tan iₚ, where iₚ is polarising angle.
11. Interference fringes are equally spaced because:
Answer: B
Path difference changes uniformly across screen.
Path difference changes uniformly across screen.
12. Missing orders in diffraction depend on:
Answer: A
Occurs when interference minima coincide with diffraction maxima.
Occurs when interference minima coincide with diffraction maxima.
13. Fringe width increases if slit separation:
Answer: B
β ∝ 1/d, so decreasing slit distance increases fringe width.
β ∝ 1/d, so decreasing slit distance increases fringe width.
14. Diffraction confirms light has:
Answer: A
Diffraction is a wave phenomenon.
Diffraction is a wave phenomenon.
15. Polarised sunglasses reduce:
Answer: B
They block horizontally polarised reflected light.
They block horizontally polarised reflected light.
16. Fringe width is maximum for:
Answer: A
β ∝ λ, and red has largest wavelength.
β ∝ λ, and red has largest wavelength.
17. Single slit diffraction minima condition:
Answer: A
a sinθ = nλ gives dark fringes.
a sinθ = nλ gives dark fringes.
18. Interference requires sources to be:
Answer: B
Coherence is essential for stable fringes.
Coherence is essential for stable fringes.
19. Width of central diffraction maximum is:
Answer: C
Central maximum is twice as wide.
Central maximum is twice as wide.
20. Nicol prism is used for:
Answer: C
It produces plane polarised light.
It produces plane polarised light.