Physics MCQs

Question #1001

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Einstein known for:

A. Electromagnetic induction

B. Discovery of electron

C. Nuclear model of atom

D. Photoelectric effect explanation

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Correct Answer: Option D

Explanation:
Einstein explained photoelectric effect (1905) using light quanta (photons), earning Nobel Prize. Also developed relativity. Electron: Thomson; Nuclear atom: Rutherford; Induction: Faraday. Memory aid: 'Einstein = photons + relativity'. Key contribution frequently tested in competitive modern physics history questions.

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Question #1002

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Assertion: Acceleration in SHM is maximum at extremes. Reason: Restoring force ∝ displacement.

A. Both true, R doesn't explain A

B. A false, R true

C. Both true, R explains A

D. A true, R false

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Correct Answer: Option C

Explanation:
Assertion true: a = -ω²x, max at max |x|. Reason true: F = -kx (Hooke's law), and F = ma ⇒ a ∝ -x. Reason correctly explains why acceleration peaks at extremes. Memory tip: 'SHM: F ∝ -x ⇒ a ∝ -x'. Assertion-reason testing SHM fundamentals, frequently examined in competitive exams.

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Question #1003

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Assertion: Pressure is scalar. Reason: Pressure acts equally in all directions at a point.

A. A true, R false

B. Both true, R explains A

C. Both true, R doesn't explain A

D. A false, R true

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Correct Answer: Option B

Explanation:
Pressure is scalar (no direction), though force is vector. Reason: Pascal's law - fluid pressure transmits equally in all directions, confirming scalar nature. Memory aid: 'Pressure = force/area (scalar division); isotropic in fluids'. Assertion-reason testing fluid mechanics fundamentals, common in competitive exams.

This question belongs to: Science Physics

Question #1004

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Body moving with constant velocity has:

A. Zero acceleration

B. Increasing acceleration

C. Variable acceleration

D. Constant acceleration

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Correct Answer: Option A

Explanation:
Constant velocity ⇒ no change in speed or direction ⇒ acceleration = dv/dt = 0. Newton's first law: zero net force for constant velocity. Memory tip: 'Constant v ⇒ a = 0; changing v ⇒ a ≠ 0'. Basic kinematics concept frequently tested to verify acceleration-velocity relationship understanding.

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Question #1005

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Dimensional formula [M⁰L⁰T⁰] represents:

A. Angle

B. Refractive index

C. All of these

D. Strain

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Correct Answer: Option C

Explanation:
Dimensionless quantities: angle (radian = arc/radius), strain (ΔL/L), refractive index (ratio of speeds). All have [M⁰L⁰T⁰]. Memory aid: 'Ratios of same dimensions ⇒ dimensionless'. Dimensional analysis question frequently tested in competitive exams to identify dimensionless physical quantities.

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Question #1006

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Convex lens forms virtual image when object is:

A. At 2F

B. Beyond 2F

C. Between F and 2F

D. Within focal length

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Correct Answer: Option D

Explanation:
Convex lens: object within focal length (u < f) produces virtual, erect, magnified image (magnifying glass). Beyond F: real images. Memory tip: 'Convex lens: u < f ⇒ virtual image; u > f ⇒ real image'. Ray optics concept frequently tested in competitive exams to verify lens image formation rules.

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Question #1007

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Light year is unit of:

A. Speed

B. Time

C. Distance

D. Luminosity

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Correct Answer: Option C

Explanation:
Light year: distance light travels in one year in vacuum ≈ 9.46×10¹⁵ m. Astronomical distance unit, not time. Memory aid: 'Light year = speed × time = distance'. Unit knowledge frequently tested in competitive exams to avoid common misconception about light year being time unit.

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Question #1008

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Potentiometer measures EMF accurately because:

A. It has high resistance

B. It uses null deflection

C. It draws no current from cell

D. Both (a) and (c)

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Correct Answer: Option D

Explanation:
Potentiometer uses null method: at balance, no current flows through cell, so measured voltage equals true EMF (no internal resistance drop). Memory aid: 'Null method ⇒ zero current ⇒ accurate EMF measurement'. Experimental physics concept frequently tested in competitive exams to verify understanding of precision measurement techniques.

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Question #1009

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de Broglie wavelength λ = h/p. For electron, λ ∝:

A. 1/v

B. v²

C. v

D. 1/v²

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Correct Answer: Option A

Explanation:
p = mv ⇒ λ = h/(mv) ⇒ λ ∝ 1/v for constant mass. Higher velocity ⇒ shorter wavelength. Memory tip: 'λ = h/mv; faster particle ⇒ smaller wavelength'. Quantum mechanics relation frequently tested in competitive modern physics sections.

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Question #1010

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Projectile horizontal range maximum at angle:

A. 30°

B. 45°

C. 90°

D. 60°

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Correct Answer: Option B

Explanation:
Range R = u²sin(2θ)/g. sin(2θ) maximum (=1) when 2θ=90° ⇒ θ=45°. Standard result for level ground projection. Memory aid: 'Max range at 45°; max height at 90°'. Projectile motion fact frequently tested in competitive exams.

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Question #1011

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Critical angle for glass (n=1.5) to air:

A. 42°

B. 60°

C. 90°

D. 30°

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Correct Answer: Option A

Explanation:
sinθ_c = n₂/n₁ = 1/1.5 = 2/3 ⇒ θ_c = sin⁻¹(0.667) ≈ 42°. Total internal reflection condition. Memory tip: 'θ_c = sin⁻¹(1/n) for denser to air'. Optics calculation frequently tested in competitive exams with standard refractive indices.

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Question #1012

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Young's double slit: fringe width β = λD/d. If d doubled, β becomes:

A. Four times

B. Half

C. Same

D. Double

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Correct Answer: Option B

Explanation:
β ∝ 1/d. If d' = 2d, β' = β/2. Fringe width decreases with increased slit separation. Memory aid: 'β ∝ 1/d; wider slit separation ⇒ narrower fringes'. Wave optics proportionality frequently tested in competitive exams.

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Question #1013

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Photoelectric threshold frequency ν₀ = φ/h. If work function doubles, ν₀:

A. Quadruples

B. Unchanged

C. Halves

D. Doubles

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Correct Answer: Option D

Explanation:
ν₀ ∝ φ. Double work function ⇒ double threshold frequency. Higher φ requires higher photon energy for emission. Memory tip: 'ν₀ = φ/h; larger φ ⇒ higher frequency needed'. Photoelectric effect relation frequently tested in competitive quantum physics sections.

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Question #1014

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Carnot efficiency η = 1 - T₂/T₁. If T₁=600K, T₂=300K, η is:

A. 100%

B. 75%

C. 50%

D. 25%

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Correct Answer: Option C

Explanation:
η = 1 - 300/600 = 1 - 0.5 = 0.5 = 50%. Maximum possible efficiency for given temperatures. Memory aid: 'η_Carnot = 1 - T_cold/T_hot; always < 100%'. Thermodynamics calculation frequently tested in competitive exams.

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Question #1015

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Electric field due to point charge: E ∝

A. r²

B. 1/r

C. r

D. 1/r²

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Correct Answer: Option D

Explanation:
Coulomb's law: E = kq/r² ⇒ E ∝ 1/r². Inverse square law fundamental to electrostatics and gravitation. Memory tip: 'Point charge field: inverse square; double distance ⇒ field becomes 1/4'. Electrostatics concept frequently tested in competitive exams.

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Question #1016

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Capacitor energy U = ½CV². If voltage doubled, energy becomes:

A. Four times

B. Double

C. Half

D. Same

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Correct Answer: Option A

Explanation:
U ∝ V². If V' = 2V, U' = 4U. Energy scales with square of voltage. Memory aid: 'Capacitor energy: U ∝ V²; double voltage ⇒ quadruple energy'. Electrostatics proportionality frequently tested in competitive exams.

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Question #1017

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Diamagnetic material susceptibility χ is:

A. Large positive

B. Small positive

C. Large negative

D. Small negative

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Correct Answer: Option D

Explanation:
Diamagnets: χ ≈ -10⁻⁵ (small negative), weakly repelled by magnetic fields. Paramagnets: small +χ; Ferromagnets: large +χ. Memory tip: 'Diamagnetic: χ < 0, weak repulsion'. Magnetism classification frequently tested in competitive exams.

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Question #1018

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Transistor current gain β = I_C/I_B. Typical value range:

A. 1000-5000

B. 0.1-1

C. 1-10

D. 20-200

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Correct Answer: Option D

Explanation:
BJT common-emitter current gain β typically 20-200. Small base current controls larger collector current. Memory aid: 'β = collector/base current ratio; value 20-200 for standard transistors'. Electronics parameter frequently tested in competitive exams.

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Question #1019

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Binding energy per nucleon peaks at:

A. Uranium

B. Hydrogen

C. Helium

D. Iron

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Correct Answer: Option D

Explanation:
Maximum binding energy/nucleon ≈ 8.8 MeV at iron-56, making it most stable. Lighter nuclei release energy via fusion; heavier via fission. Memory tip: 'Iron peak: most stable nucleus; fusion before, fission after'. Nuclear physics concept frequently tested in competitive exams.

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Question #1020

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Spring-mass period T = 2π√(m/k). If mass quadrupled, T becomes:

A. Half

B. Four times

C. Same

D. Double

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Correct Answer: Option D

Explanation:
T ∝ √m. If m' = 4m, T' = √4 × T = 2T. Period doubles when mass quadruples. Memory aid: 'Spring period: T ∝ √m; 4× mass ⇒ 2× period'. Oscillations proportionality frequently tested in competitive exams.

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