Engineering Physics Unit 3 – Wave Optics: important questions for AKTU
Unit 3 (Wave Optics) questions that AKTU repeats most often. This unit carries about 28 marks per paper. Start with the repeated questions, then the most asked topics.
Most repeated Unit 3 questions
- Explain interference in thin films due to reflected light of uniform thickness and obtain the condition of bright and dark rings. (7 marks, 2025, Interference of Light) – also asked in 2022, 2023, 2024, 2025
- A parallel beam of sodium light of wavelength 5880 Å is incident on a thin glass plate of refractive index 1.5 such that the angle of refraction in plate is 60°. Calculate the smallest thickness of the plate, which will make it appear dark by reflection. (7 marks, 2025, Interference of Light) – also asked in 2022, 2023, 2024, 2025
- Give the construction and theory of plane transmission grating and explain the formation of spectra by it. (7 marks, 2024, Diffraction Grating) – also asked in 2021, 2023, 2025, 2026
Most important Unit 3 topic
- Interference of Light (Unit 3: Wave Optics) – asked 26 times in 2021, 2022, 2023, 2024, 2025, 2026
Most asked Unit 3 topics
- Interference of Light – asked 26 times
- Diffraction of Light – asked 10 times
- Diffraction Grating – asked 8 times
More Unit 3 previous year questions
- For a plane transmission grating with 5000 lines/cm, determine the highest order of spectrum observable with light of 6000 Å. (2 marks, 2026, Diffraction Grating)
- Discuss the formation of interference fringes due to a thin wedge-shaped film as seen by normally reflected sodium light. Derive an expression for the fringe width. (7 marks, 2026, Interference of Light)
- Explain and obtain the condition of absent spectra in plane transmission grating. If the width d of the opaque space (ruling) is equal to the width e of the transparent space, which orders will be absent? Which if d = 2e? (7 marks, 2026, Diffraction of Light)
- Discuss Fraunhofer Diffraction of light at a double slit and obtain the conditions for diffraction and interference maxima and minima. (7 marks, 2026, Diffraction of Light)
- Define Dispersive power of grating. (2 marks, 2025, Diffraction Grating)
Unit 3 syllabus topics
- Interference of Light
- Diffraction of Light
- Diffraction Grating
- Rayleigh Criterion Resolution