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NEET UG Wave Optics — practice questions

Explore 87 free Wave Optics questions in NEET UG Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Wave Optics questions and exercises with answers

Showing questions 1–30 of 87.

Two crossed polaroids transmit light of intensity:Read the answer and worked solution →The refractive index of glass is 1.5. The speed of light in glass is:Read the answer and worked solution →Two point charges q₁ and q₂ separated by distance r in vacuum experience force F. If both charges are doubled AND the distance is halved, the new force is:Read the answer and worked solution →The SI unit of electric field is:Read the answer and worked solution →A dipole of moment p is placed in a uniform external field E. The torque on the dipole is:Read the answer and worked solution →A dipole of moment 10⁻²⁹ C·m is placed in a uniform field of 10⁵ N/C at angle 30°. The torque on the dipole is:Read the answer and worked solution →For a uniformly charged thin spherical shell of radius R and total charge Q, the electric field INSIDE the shell (r < R) is:Read the answer and worked solution →Linear charge density λ has SI units:Read the answer and worked solution →The Lorentz force on a charge q moving with velocity v in fields E and B is:Read the answer and worked solution →The force on a charge q moving with speed v perpendicular to a magnetic field B has magnitude:Read the answer and worked solution →Light passes from air to glass ($n = 1.5$). Brewster's angle is:Read the answer and worked solution →HUYGENS' PRINCIPLE states that every point on a wavefront acts as a:Read the answer and worked solution →In Young's double-slit experiment, the fringe width β is given by:Read the answer and worked solution →In Young's experiment, a BRIGHT fringe (constructive interference) requires path difference = ?Read the answer and worked solution →In single-slit diffraction, the central maximum is:Read the answer and worked solution →Polarisation of light is direct experimental evidence that light is a:Read the answer and worked solution →BREWSTER'S LAW for the polarising angle θ_B relates to the refractive index n as:Read the answer and worked solution →The resolving power (RP) of a diffraction grating with N slits in the m-th order is:Read the answer and worked solution →NEET · Physics · Interference or DiffractionRead the answer and worked solution →In a double-slit experiment, if the wavelength is doubled and the slit separation is halved, the fringe width becomesRead the answer and worked solution →At a point where the path difference between two coherent light waves is 3λ/2, the interference isRead the answer and worked solution →The Huygens principle states that every point of a wavefront acts asRead the answer and worked solution →For diffraction at a single slit of width a, the angular position of the first minimum is given byRead the answer and worked solution →The width of the central maximum in single-slit diffraction on a screen at distance D isRead the answer and worked solution →The polarising angle (Brewster angle) for glass of refractive index 1.5 isRead the answer and worked solution →Which of the following phenomena is characteristic ONLY of transverse waves and NOT of longitudinal waves?Read the answer and worked solution →An unpolarised light of intensity I₀ passes through a polariser. The transmitted intensity isRead the answer and worked solution →If polarised light of intensity I passes through a polariser whose axis makes angle θ with the polarisation direction, the transmitted intensity by Malus's law isRead the answer and worked solution →Coherent sources are those that emit waves ofRead the answer and worked solution →Newton originally supported the corpuscular theory of light. The wave theory was strongly established byRead the answer and worked solution →

Worked practice questions

Two crossed polaroids transmit light of intensity:

  1. I₀ (full intensity)
  2. Zero — because cos²(90°) = 0; no light gets through
  3. I₀/2
  4. I₀/4
Show answer and solution

Correct answer: B. Zero — because cos²(90°) = 0; no light gets through

**Crossed polaroids (pass-axes at 90°)**: I_transmitted = I_polarised × cos²(90°) = **0**. Complete extinction. This is the basis of polarimeters and 3D glasses (where each lens passes only one polarisation).

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The refractive index of glass is 1.5. The speed of light in glass is:

  1. 3 × 10⁸ m/s
  2. 2 × 10⁸ m/s (since v = c/n = 3 × 10⁸ / 1.5)
  3. 4.5 × 10⁸ m/s
  4. 1.5 × 10⁸ m/s
Show answer and solution

Correct answer: B. 2 × 10⁸ m/s (since v = c/n = 3 × 10⁸ / 1.5)

We have **v = c/n. That is **v = 3 × 10⁸ / 1.5. So **v = 2 × 10⁸ m/s**. Light travels slower in any normal medium than in vacuum. *Note: violet light slows MORE than red (n_violet > n_red — dispersion).*

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Two point charges q₁ and q₂ separated by distance r in vacuum experience force F. If both charges are doubled AND the distance is halved, the new force is:

  1. 4F
  2. 8F
  3. 16F
  4. 2F
Show answer and solution

Correct answer: C. 16F

F ∝ q₁q₂/r². **New:** F' ∝ (2q₁)(2q₂)/(r/2)² = 4 × 4 × F = **16F**. Each doubling of charge contributes factor 2 (so 4 total), halving distance contributes factor 4. 4 × 4 = 16.

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More Physics topics

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