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Wave Optics — NEET Physics MCQs

30 questions written by hand against the NCERT chapter. Every wrong option is explained, not just the right one.

30questions
10/14/6easy / medium / hard
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Sample questions from this chapter

What is a wavefront?
  1. A surface of constant phase ✓
  2. The path followed by one photon
  3. A surface of constant intensity only
  4. The line joining a source to an observer
Answer: A. A wavefront is the locus of points oscillating with the same phase; energy propagates normal to it.
Why not B: A ray describes propagation direction, whereas a wavefront contains many in-phase points.
Why not C: Equal amplitude may occur on ideal spherical fronts, but phase defines a wavefront.
Why not D: A source-observer line is a ray normal to the wavefront, not the front itself.
An entire Young double-slit apparatus is immersed in a liquid of refractive index n without changing its geometry. How does fringe width change?
  1. It becomes nβ because d decreases
  2. It remains β because frequency is unchanged
  3. It becomes β/n because wavelength decreases ✓
  4. It becomes β/n² because both λ and d decrease
Answer: C. In the liquid λ′=λ/n while D and d stay fixed, so β′=λ′D/d=β/n.
Why not A: The physical slit separation does not contract on immersion, and wavelength decreases.
Why not B: Frequency stays fixed, but the reduced speed lowers wavelength and fringe width.
Why not D: Only optical wavelength changes; d is a geometric distance.
In a Young experiment, d=0.280 mm and D=1.40 m. The fourth bright fringe is 1.20 cm from the central maximum. What wavelength is used?
  1. 600 nm ✓
  2. 800 nm
  3. 480 nm
  4. 1200 nm
Answer: A. x₄=4λD/d, so λ=xd/(4D)=(0.0120)(2.80×10⁻⁴)/(4×1.40)=600 nm.
Why not B: This calls the central maximum the first bright fringe and therefore uses order n=3.
Why not C: This uses five fringe intervals between the centre and fourth bright fringe.
Why not D: This uses only two intervals and overestimates wavelength by two.

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Questions

How many NEET questions are there on Wave Optics?

This chapter test has 30 questions — 10 easy, 14 medium and 6 hard — all written against the NCERT Class 12 chapter.

Is this NEET Physics chapter test free?

Yes. Every chapter test is free with no login, and you get your all-India rank on every one. Nothing on the site is on sale right now.

Do the questions explain the wrong options?

Yes — every distractor carries its own explanation naming the specific misconception that makes a student pick it. That is the part most question banks skip, and it is the part that changes your next attempt.