Engineering Physics Unit 3 – Wave Optics: AKTU previous year questions
48 AKTU questions from Unit 3 (Wave Optics) asked in 2021–2026, tagged by marks, year and topic. In short: about 28 marks of every paper come from this unit; the most asked topic is Interference of Light (26 times); 44 questions came back in a later year. The latest ones are listed below; on the page you can filter them by 2-mark or long questions, topic and repeats.
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)
- Centre is dark in Newton's rings experiment. Explain it. (2 marks, 2025, Interference of Light)
- Derive the conditions of Maxima & Minima in reflected light in a thin film of uniform thickness. (7 marks, 2025, Interference of Light)
- 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)
- Derive Expression for diameter of dark ring in Newton's rings. (7 marks, 2025, Interference of Light)
- Discuss Fraunhofer diffraction of light at a double slit and obtain the conditions for diffraction and interference maxima and minima. (7 marks, 2025, Diffraction of Light)
- Discuss the phenomenon of Fraunhofer diffraction at a single slit. Show that the intensity of first subsidiary maximum is about 4.5% of the principal maximum. (7 marks, 2025, Diffraction of Light)
- 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)
Most asked Unit 3 topics
- Interference of Light – asked 26 times
- Diffraction of Light – asked 10 times
- Diffraction Grating – asked 8 times
Unit 3 question pattern
- 2-mark questions: 15 asked in 2021–2026
- 7-mark questions: 24 asked in 2021–2026
- 10-mark questions: 9 asked in 2021–2026
- About 28 marks from Unit 3 in every paper
- 44 questions were asked again in a later year
Unit 3 questions year by year
- 2026: 4 Unit 3 questions asked (23 marks across that year's papers)
- 2025: 9 Unit 3 questions asked (53 marks across that year's papers)
- 2024: 11 Unit 3 questions asked (62 marks across that year's papers)
- 2023: 9 Unit 3 questions asked (48 marks across that year's papers)
- 2022: 10 Unit 3 questions asked (68 marks across that year's papers)
- 2021: 5 Unit 3 questions asked (34 marks across that year's papers)