Physics MCQs

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Physics MCQs

Practice the latest Physics MCQs with answers and detailed explanations. This section includes chapter-wise multiple-choice questions covering mechanics, motion, force, work and energy, heat, light, electricity, magnetism, modern physics, waves, optics, and other important topics. These exam-oriented MCQs are ideal for Class 9–12, NEET, JEE, CUET, SSC, Banking, Railway, JKSSB, Defence, Police, and other competitive exams.

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Page 34 of 65
Question #661
The phenomenon of diffraction limits the resolving power of optical instruments because:
A. Atmospheric turbulence distorts light
B. Mirrors reflect imperfectly
C. Light bends around edges, causing image blurring
D. Lenses absorb light
Discuss
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Correct Answer: Option C

Explanation:
Diffraction causes light waves to spread when passing through apertures or around obstacles, creating Airy patterns instead of point images. This fundamental wave effect limits the minimum resolvable detail (Rayleigh criterion: θ_min ≈ 1.22λ/D). Options B, C, D are practical limitations but not the fundamental diffraction limit. Memory tip: 'Diffraction limit: smaller λ or larger aperture ⇒ better resolution'. This wave optics concept is frequently tested in competitive exams. Always distinguish fundamental limits (diffraction) from technical limitations (aberrations, turbulence) in instrument performance.
This question belongs to: Science Physics
Question #662
The work done by a conservative force in moving a particle along a closed path is:
A. Zero
B. Negative
C. Positive
D. Depends on path
Discuss
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Correct Answer: Option A

Explanation:
Conservative forces (gravity, spring, electrostatic) have path-independent work; work done over any closed loop is zero. This defines conservative forces and enables potential energy definition. Non-conservative forces (friction) have non-zero closed-path work. Memory aid: 'Conservative force: ∮F·dr = 0; enables energy conservation'. This mechanics concept is frequently tested in competitive exams. Always link conservative forces to potential energy and mechanical energy conservation; this is foundational for advanced physics problem-solving.
This question belongs to: Science Physics
Question #663
The phenomenon of polarization cannot occur in:
A. Sound waves
B. X-rays
C. Radio waves
D. Light waves
Discuss
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Correct Answer: Option A

Explanation:
Polarization requires transverse waves (oscillations perpendicular to propagation). Light, radio waves, X-rays are electromagnetic transverse waves and can be polarized. Sound waves in air are longitudinal (oscillations parallel to propagation) and cannot be polarized. Memory tip: 'Polarization ⇒ transverse waves only; sound is longitudinal ⇒ no polarization'. This wave property question tests understanding of wave types, frequently examined in competitive exams. Always classify waves as transverse/longitudinal to determine polarization possibility; this is a common conceptual trap.
This question belongs to: Science Physics
Question #664
The time taken for a ball dropped from height h to reach ground is t. If dropped from height 4h, the time taken is:
A. 2t
B. t/2
C. t
D. 4t
Discuss
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Correct Answer: Option A

Explanation:
Free fall: h = ½gt² ⇒ t = √(2h/g). Thus t ∝ √h. If h' = 4h, t' = √(4h/g) = 2√(h/g) = 2t. Time doubles when height quadruples. Memory aid: 'Free fall time: t ∝ √h; quadruple height ⇒ double time'. This kinematics proportional reasoning problem is frequently tested in competitive exams. Always derive the proportionality from fundamental equations; avoid assuming linear relationships for non-linear motion.
This question belongs to: Science Physics
Question #665
The phenomenon of resonance in an LCR circuit occurs when:
A. Resistance is zero
B. Impedance is maximum
C. Inductive reactance equals capacitive reactance
D. Frequency is zero
Discuss
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Correct Answer: Option C

Explanation:
Resonance in series LCR circuit occurs when X_L = X_C, i.e., ωL = 1/(ωC) ⇒ ω = 1/√(LC). At this frequency, impedance is minimum (Z=R), current maximum, and circuit is purely resistive. Memory tip: 'Resonance: X_L = X_C; ω₀ = 1/√(LC); series: Z_min, parallel: Z_max'. This AC circuit concept is frequently tested in competitive exams. Always distinguish series and parallel resonance conditions; competitive exams often test series LCR resonance fundamentals.
This question belongs to: Science Physics
Question #666
The specific latent heat of fusion of ice is 336 kJ/kg. The heat required to melt 2 kg of ice at 0°C is:
A. 168 kJ
B. 1344 kJ
C. 672 kJ
D. 336 kJ
Discuss
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Correct Answer: Option C

Explanation:
Heat for phase change Q = m·L_f, where L_f is latent heat of fusion. Thus Q = 2 kg × 336 kJ/kg = 672 kJ. This direct application tests calorimetry fundamentals. Memory aid: 'Latent heat: Q = mL; no temperature change during phase transition'. Competitive exams frequently test such calculations with standard values. Always ensure units match (kg and kJ/kg here); convert if necessary. This problem assesses basic formula application skills essential for thermodynamics sections.
This question belongs to: Science Physics
Question #667
The phenomenon of dispersion of light occurs because:
A. Different colors have different frequencies
B. Prism absorbs some colors
C. Different colors travel at different speeds in medium
D. Total internal reflection occurs
Discuss
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Correct Answer: Option C

Explanation:
Dispersion (splitting of white light into colors) occurs because refractive index n varies with wavelength (Cauchy's relation: n ∝ 1/λ² approximately). Since v = c/n, different colors travel at different speeds in the medium, causing different refraction angles (Snell's law). Frequency remains constant across media. Memory tip: 'Dispersion: n(λ) ⇒ v(λ) ⇒ different bending; violet bends most (highest n)'. This optics concept is frequently tested in competitive exams. Always distinguish cause (speed variation) from property (frequency/wavelength); competitive exams often test this nuanced understanding.
This question belongs to: Science Physics
Question #668
The time period of a simple pendulum is measured as 2.0 s with an error of 0.1 s. The percentage error in the calculated value of g is approximately:
A. 20%
B. 2.5%
C. 5%
D. 10%
Discuss
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Correct Answer: Option D

Explanation:
Pendulum period T = 2π√(l/g) ⇒ g = 4π²l/T². For error propagation, % error in g = % error in l + 2 × % error in T. Assuming l measured precisely, % error in g ≈ 2 × (% error in T). % error in T = (0.1/2.0)×100% = 5%. Thus % error in g ≈ 2×5% = 10%. Memory tip: 'g ∝ 1/T² ⇒ %Δg = 2 × %ΔT'. This error analysis problem tests experimental physics skills, frequently appearing in competitive exams. Always apply power rule for error propagation: if Q ∝ xⁿ, %ΔQ = |n| × %Δx.
This question belongs to: Science Physics
Question #669
The phenomenon of electromagnetic induction is the basis for the working of:
A. Electric motor
B. Transformer
C. Both (b) and (c)
D. Generator
Discuss
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Correct Answer: Option C

Explanation:
Electromagnetic induction (changing magnetic flux induces EMF) is the principle behind generators (mechanical energy to electrical) and transformers (AC voltage conversion). Electric motors work on the reverse principle: force on current-carrying conductor in magnetic field. Memory aid: 'Induction applications: generators, transformers, induction cooktops; motors use motor effect'. This application question tests electromagnetism fundamentals, frequently examined in competitive exams. Always distinguish induction (generator/transformer) from motor effect (motor); competitive exams often combine both in device-based questions.
This question belongs to: Science Physics
Question #670
The work done in moving a unit positive charge between two points in an electric field is called:
A. Electric potential
B. Capacitance
C. Electric potential energy
D. Electric field intensity
Discuss
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Correct Answer: Option A

Explanation:
Electric potential V at a point is defined as work done per unit charge to bring a test charge from infinity to that point: V = W/q. Thus potential difference between two points is work per unit charge to move between them. Electric field intensity is force per unit charge; potential energy is work to assemble charges; capacitance is charge storage ability. Memory tip: 'Potential = work per unit charge; field = force per unit charge'. This definition-based question tests electrostatics fundamentals, frequently appearing in competitive exams. Always distinguish potential (scalar, work/charge) from field (vector, force/charge).
This question belongs to: Science Physics
Question #671
The phenomenon of beats can be observed when two sound waves have:
A. Very different frequencies
B. Same frequency but different amplitudes
C. Same frequency and amplitude
D. Slightly different frequencies
Discuss
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Correct Answer: Option D

Explanation:
Beats occur due to interference of two waves with slightly different frequencies (Δf small, typically < 10 Hz for audible beats). The beat frequency is |f₁ - f₂|, causing periodic loudness variation. Same frequency (A, B) produces steady interference (no beats); very different frequencies (D) produce rapid fluctuations not perceived as beats. Memory aid: 'Beats: |f₁ - f₂| small ⇒ audible pulsations; used in tuning'. This wave phenomenon question tests superposition understanding, frequently examined in competitive exams. Always link beat perception to frequency difference magnitude; competitive exams often test qualitative conditions for observable beats.
This question belongs to: Science Physics
Question #672
The time period of revolution of a geostationary satellite is:
A. 12 hours
B. 84 minutes
C. 24 hours
D. Variable
Discuss
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Correct Answer: Option C

Explanation:
Geostationary satellites orbit in Earth's equatorial plane with period matching Earth's rotation period (24 hours), so they appear stationary relative to ground. Orbital radius is about 42,000 km from Earth's center. Memory tip: 'Geostationary: T=24 h, equatorial orbit, fixed position; used for communication/weather satellites'. This standard result is frequently tested in competitive exams. Always recall that geostationary is a special case of geosynchronous (same period) with zero inclination; competitive exams often compare low orbit (84 min) vs geostationary (24 h) periods.
This question belongs to: Science Physics
Question #673
The phenomenon of total internal reflection requires the light to travel from:
A. Water to glass
B. Glass to air
C. Air to glass
D. Any medium to vacuum
Discuss
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Correct Answer: Option B

Explanation:
Total internal reflection (TIR) occurs only when light travels from denser medium to rarer medium (e.g., glass to air, water to air) and angle of incidence exceeds critical angle. Air to glass (A) causes refraction toward normal; water to glass (C) may or may not cause TIR depending on refractive indices; vacuum is rarer than any medium but TIR requires denser→rarer. Memory aid: 'TIR condition: denser→rarer AND i > θ_c'. This optics condition question is frequently tested in competitive exams. Always verify both conditions (medium order and angle) for TIR; competitive exams often test common misconceptions about direction of travel.
This question belongs to: Science Physics
Question #674
The phenomenon of diffraction is evidence for the:
A. Electromagnetic nature of light
B. Wave nature of light
C. Dual nature of light
D. Particle nature of light
Discuss
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Correct Answer: Option B

Explanation:
Diffraction (bending of waves around obstacles) is a characteristic wave phenomenon, explained by Huygens' principle and wave superposition. It demonstrates light's wave nature, as particles would travel in straight lines. Particle nature is shown by photoelectric effect; dual nature combines both. Memory aid: 'Diffraction/interference ⇒ wave nature; photoelectric effect ⇒ particle nature'. This conceptual question tests wave-particle duality fundamentals, frequently examined in competitive exams. Always link specific phenomena to the aspect of light they demonstrate; competitive exams often combine both aspects in advanced questions requiring nuanced understanding.
This question belongs to: Science Physics
Question #675
The phenomenon of resonance in sound is used in:
A. Neither
B. Both (a) and (b)
C. Tuning forks
D. Musical instruments
Discuss
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Correct Answer: Option B

Explanation:
Resonance (amplification at natural frequency) is exploited in musical instruments (e.g., guitar body resonates with string frequencies) and tuning forks (designed to vibrate at precise frequency for calibration). Memory tip: 'Resonance applications: musical instruments (amplify sound), tuning forks (frequency standard), bridges (avoid resonance to prevent collapse)'. This application question tests wave phenomena uses, frequently appearing in competitive exams. Always link physical principles to practical applications; competitive exams emphasize real-world relevance of physics concepts, including both beneficial and hazardous aspects of resonance.
This question belongs to: Science Physics
Question #676
The time period of a simple pendulum is independent of:
A. Acceleration due to gravity
B. Length of pendulum
C. Mass of bob
D. Amplitude (for small angles)
Discuss
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Correct Answer: Option C

Explanation:
Pendulum period T = 2π√(l/g) for small amplitudes. It depends on length l and gravity g, but not on bob mass or amplitude (isochronism for small angles). Mass independence arises because gravitational force and inertia both proportional to mass, canceling out. Memory aid: 'Pendulum: T ∝ √(l/g); independent of mass and small-amplitude'. This conceptual question tests oscillations fundamentals, frequently examined in competitive exams. Always verify the small-angle approximation; competitive exams assume it unless specified otherwise. This problem assesses understanding of which parameters affect periodic motion.
This question belongs to: Science Physics
Question #677
The phenomenon of polarization is used in:
A. LCD displays
B. Neither
C. Sunglasses to reduce glare
D. Both (a) and (b)
Discuss
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Correct Answer: Option D

Explanation:
Polarized sunglasses use polarizing filters to block horizontally polarized glare reflected from surfaces (water, roads). LCD displays use liquid crystals to rotate polarization, controlling light transmission through polarizers. Memory tip: 'Polarization applications: glare reduction (sunglasses), display technology (LCDs), 3D movies'. This application question tests wave optics uses, frequently appearing in competitive exams. Always link physical principles to everyday technologies; competitive exams emphasize practical relevance of physics concepts, making abstract phenomena tangible through common devices.
This question belongs to: Science Physics
Question #678
The work done by the gravitational force when a body is moved horizontally on Earth's surface is:
A. Negative
B. Positive
C. Zero
D. Depends on speed
Discuss
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Correct Answer: Option C

Explanation:
Gravitational force acts vertically downward. For horizontal displacement, the angle between force and displacement is 90°, so work W = F·d·cos90° = 0. Gravity does no work for horizontal motion; it only does work for vertical displacement components. Memory aid: 'Work = F d cosθ; θ=90° ⇒ W=0'.
This question belongs to: Science Physics
Question #679
Which of the following is not a fundamental unit in SI?
A. Ampere
B. Kilogram
C. Newton
D. Kelvin
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Correct Answer: Option C

Explanation:
Fundamental units: kg, m, s, A, K, mol, cd. Newton is derived (kg m/s²). Therefore, Newton is not fundamental. Remember the seven base units.
This question belongs to: Science Physics
Question #680
The number of significant figures in 0.00450 is
A. 3
B. 5
C. 4
D. 2
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Correct Answer: Option A

Explanation:
Leading zeros not significant. '450' has three digits, but the trailing zero after decimal is significant (4,5,0). So 3 significant figures. 0.00450 is 3 SF.
This question belongs to: Science Physics

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