A heat engine absorbs 1000 J from a hot reservoir and rejects 600 J to a cold reservoir in one cycle. Its efficiency is:

The correct answer is A: 40%. Efficiency η = W/Q_h = (Q_h − Q_c)/Q_h = (1000 − 600)/1000 = 400/1000 = 0.40 = 40%

A sound wave traveling in air at 340 m/s encounters a wall. The reflected wave interferes with the incident wave. At what distance from the wall is the first antinode?

The correct answer is A: λ/4. For a wall (fixed boundary), phase reversal occurs. Antinode forms at λ/4 from the wall

An ideal gas undergoes an adiabatic process from state (P₁, V₁, T₁) to (P₂, V₂, T₂) with γ = 1.4. If volume increases by 50%, the temperature ratio T₂/T₁ is approximately:

The correct answer is B: 0.73. For adiabatic process: TV^(γ-1) = constant. T₁V₁^0.4 = T₂(1.5V₁)^0.4. T₂/T₁ = (1/1.5)^0.4 = 0.73^0.4 ≈ 0.73

An electron transitions from n=3 to n=1 in hydrogen atom. The frequency of emitted photon is (R = 1.097×10⁷ m⁻¹):

The correct answer is A: 2.47×10¹⁵ Hz. ν = Rc(1/n₁² - 1/n₂²) = 1.097×10⁷ × 3×10⁸ × (1 - 1/9) = 1.097×10¹⁵ × 8/9 ≈ 2.47×10¹⁵ Hz

A spherical shell of radius R carries a uniformly distributed charge Q. What is the electric field inside the shell at distance r from the center (r < R)?

The correct answer is A: E = 0. By Gauss's law, for a uniformly charged spherical shell, the electric field inside (r < R) is zero because the enclosed charge is zero.

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JEE Physics
Optics

Physics questions for JEE Main — Mechanics, Electrostatics, Optics, Modern Physics.

31 Q 9 Topics Take Mock Test

Difficulty: All Easy Medium Hard 31–31 of 31

Topics in JEE Physics

All Mechanics 100 Thermodynamics 100 Electrostatics 100 Current Electricity 100 Magnetism 100 Optics 100 Modern Physics 100 Semiconductors 100 Waves 100

Q.31 Easy Optics

A light ray travels from air into glass with refractive index 1.5. If the angle of incidence is 30°, what is the angle of refraction?

A 19.47°

B 22.08°

C 25.5°

D 30°

Correct Answer: A. 19.47°

EXPLANATION

Using Snell's law: n₁sin(θ₁) = n₂sin(θ₂). 1×sin(30°) = 1.5×sin(θ₂). sin(θ₂) = 0.5/1.5 = 1/3. θ₂ = 19.47°

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JEE Physics
Optics