Electromagnetic WavesNEET MCQs with solutions
Electromagnetic Waves covers the EM spectrum, properties of EM waves, displacement current and Maxwell's equations. NEET tests the EM spectrum order (frequency, wavelength, uses), properties of EM waves and displacement current concept — mostly conceptual and factual.
- Class
- 12 Physics
- Free on this page
- 24 questions
- In the RankUp app
- 399 questions
- ELITE questions
- 131
- NCERT topics
- 13
Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Grand Test
A plane electromagnetic wave travels in free space with electric-field amplitude 48 V m⁻¹. Taking c = 3 × 10⁸ m s⁻¹, what is the magnetic-field amplitude?
Not quite — the answer is B.
B₀ = E₀/c = 48/(3 × 10⁸) = 1.6 × 10⁻⁷ T. Option A traps students who slip one power of ten. Option C arises from using 3 × 10⁷ in the denominator by error.
Q2Mixed Revision
A plane electromagnetic wave in vacuum has electric-field amplitude 36 V m⁻¹. Taking c = 3 × 10⁸ m s⁻¹, its magnetic-field amplitude is:
Not quite — the answer is A.
B₀ = E₀/c = 36/(3 × 10⁸) = 1.2 × 10⁻⁷ T. Option B is a one-decade slip (×10 error). Option C comes from computing E₀ × c instead of E₀/c. Option D uses c = 10⁹ m/s by mistake.
Q3PYQ Mixed Concepts
In a plane electromagnetic wave travelling in free space, the electric field component oscillates sinusoidally at a frequency of 2.0 × 10¹⁰ Hz and has amplitude 48 V m⁻¹. The amplitude of the oscillating magnetic field is:
Not quite — the answer is C.
B₀ = E₀/c = 48/(3 × 10⁸) = 1.6 × 10⁻⁷ T. Option A is wrong by factor of 10 (common c-exponent slip). Frequency is irrelevant to B₀ calculation — a classic distractor trap.
Q4Electromagnetic Spectrum
The wavelength range of visible light in the electromagnetic spectrum is approximately:
Not quite — the answer is A.
Visible light occupies 400–700 nm. Below 400 nm is UV; above 700 nm is infrared. Option B is the UV range; option C is infrared. This is a direct NCERT fact.
Q5Radio Waves
A radio transmitter operates at a frequency of 1.368 MHz. Taking c = 3 × 10⁸ m/s, the wavelength of the emitted radiation is closest to:
Not quite — the answer is B.
λ = c/f = (3×10⁸)/(1.368×10⁶) ≈ 219.3 m, placing this in the AM radio band. The trap is mishandling the MHz conversion and obtaining 21.93 m or 2193 m instead.
Q6Microwaves
A microwave signal has a frequency of 3 × 10⁹ Hz. Its wavelength in vacuum is:
Not quite — the answer is C.
λ = c/f = (3×10⁸)/(3×10⁹) = 10⁻¹ m = 10 cm. The trap is misreading 10⁻¹ m as 10⁻² m and choosing 1 cm instead.
Q7Infrared Rays
The radiation emitted by the human body at ordinary temperatures predominantly lies in which region of the electromagnetic spectrum?
Not quite — the answer is B.
Thermal radiation from a body at ordinary temperature peaks in the infrared region. This is why infrared cameras can detect humans in darkness. UV and X-rays require much higher source temperatures.
Q8Ultraviolet Rays
Which property of ultraviolet radiation makes it useful for sterilisation?
Not quite — the answer is A.
UV photons have higher frequency and energy than visible photons (E = hf). This energy is sufficient to break DNA bonds in microorganisms, making UV effective for germicidal applications. Options B and C state properties that are factually opposite to UV characteristics.
Q9X-Rays
The energy of an electromagnetic photon is of the order of 15 keV. To which region of the EM spectrum does it belong?
Not quite — the answer is C.
X-rays span roughly 100 eV to 100 keV in photon energy. UV photons carry only a few eV and gamma-ray photons exceed 100 keV. A 15 keV photon falls squarely in the X-ray range.
Q10Gamma Rays
Which electromagnetic radiation has the highest frequency and shortest wavelength in the EM spectrum?
Not quite — the answer is A.
Gamma rays occupy the extreme high-frequency, short-wavelength end of the EM spectrum. From c = fλ in vacuum, highest frequency corresponds to shortest wavelength. X-rays are the closest but still lower in frequency than gamma rays.
Q11Electromagnetic Wave Applications
Which electromagnetic waves are most commonly used for long-distance radio and television communication?
Not quite — the answer is A.
Radio waves are used for broadcasting and long-distance communication due to their suitable atmospheric propagation and ability to carry modulated signals over large distances. All other options either lack propagation range or are unsuitable for communication modulation.
Q12Nature of Electromagnetic Waves
In a plane electromagnetic wave travelling in vacuum, the electric-field amplitude is 48 V/m. If c = 3 × 10⁸ m/s, the magnetic-field amplitude is:
Not quite — the answer is B.
Use E₀/B₀ = c, so B₀ = 48/(3 × 10⁸) = 1.6 × 10⁻⁷ T. Option A arises from dividing by c² instead of c. Option C misplaces the decimal by one power.
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Get RankUp on Google PlayQ13Visible Light
Which statement correctly describes visible light in the electromagnetic spectrum?
Not quite — the answer is A.
Visible light lies between IR and UV in the EM spectrum. Its wavelength is shorter than IR and longer than UV. It is electromagnetic and travels through vacuum.
Q14Nature of Electromagnetic Waves
For a plane electromagnetic wave in vacuum, the ratio of magnetic-field amplitude B₀ to electric-field amplitude E₀ is:
Not quite — the answer is A.
Since E₀/B₀ = c, we get B₀/E₀ = 1/c. Option B (c) is the inverse ratio E₀/B₀. Option D is the intrinsic impedance of vacuum, not the E-B ratio.
Q15Nature of Electromagnetic Waves
An electromagnetic wave is produced. Which of the following is the CORRECT condition for its generation?
Not quite — the answer is B.
Electromagnetic waves are produced by accelerating charges that create time-varying electric and magnetic fields. Constant-velocity charges do not radiate. Option D is a trap: net zero acceleration means no radiation.
Q16Nature of Electromagnetic Waves
An electromagnetic wave has electric-field amplitude E₀. If the amplitude becomes 2E₀ with frequency unchanged, the new magnetic-field amplitude in vacuum is:
Not quite — the answer is D.
Since E₀/B₀ = c (constant in vacuum), B₀ is directly proportional to E₀. Doubling E₀ doubles B₀. Students choosing B₀ (option C) incorrectly believe B₀ is set only by frequency.
Q17Nature of Electromagnetic Waves
Which of the following correctly describes a plane electromagnetic wave propagating in vacuum?
Not quite — the answer is B.
In a plane EM wave: E ⊥ B, both ⊥ propagation direction, and E and B oscillate in phase. Option C is a common confusion with mechanical waves where displacement and velocity can be out of phase.
Q18Nature of Electromagnetic Waves
Consider four statements about a plane electromagnetic wave in vacuum: I. E is perpendicular to B. II. E and B are perpendicular to the direction of propagation. III. E and B are in phase. IV. E and B have different frequencies. How many statements are CORRECT?
Not quite — the answer is C.
Statements I, II and III are correct. E ⊥ B, both are transverse to propagation, and they oscillate in phase. Statement IV is false — E and B have the same frequency in an electromagnetic wave.
Q19Nature of Electromagnetic Waves
Which of the following statements about a plane electromagnetic wave propagating through vacuum is INCORRECT?
Not quite — the answer is D.
E and B always differ in SI unit amplitude (V/m vs T) and satisfy E₀/B₀ = c. They cannot have equal numerical values in SI. Statements A, B and C are all correct properties of EM waves.
Q20Nature of Electromagnetic Waves
For a plane electromagnetic wave propagating along +z-axis in vacuum, which representation is CORRECT?
Not quite — the answer is A.
In option A, î × ĵ = k̂ (propagation along +z). Option B is wrong as k̂ is along z, not transverse. Option D gives propagation along ĵ × î = −k̂ (−z direction). Students often forget to verify E × B = propagation direction.
Q21Nature of Electromagnetic Waves
In a plane electromagnetic wave in vacuum, the ratio of average electric energy density to average magnetic energy density is:
Not quite — the answer is C.
Average electric energy density uE = ε₀E²/2 and magnetic uB = B²/2μ₀. Since E = cB and c² = 1/μ₀ε₀, these are equal. Option D (c:1) arises from confusing energy density ratio with E/B ratio.
Q22Nature of Electromagnetic Waves
Which of the following CANNOT produce a propagating electromagnetic wave?
Not quite — the answer is D.
Constant velocity means zero acceleration — no radiation. Options A, B and C all involve acceleration or time-varying currents that produce EM waves. Students often choose A thinking only large structures radiate.
Q23Nature of Electromagnetic Waves
A plane electromagnetic wave in vacuum has electric-field amplitude 6 × 10⁻² V/m. The amplitude of the associated magnetic field is:
Not quite — the answer is A.
B₀ = E₀/c = (6 × 10⁻²)/(3 × 10⁸) = 2 × 10⁻¹⁰ T. Option B results from dividing only the coefficient and ignoring the 10⁻² factor. Option D is the trap of equating B₀ = E₀ numerically.
Q24Nature of Electromagnetic Waves
In a plane electromagnetic wave, the electric and magnetic fields reach their maximum values simultaneously at a given point because:
Not quite — the answer is B.
E and B are in phase in a plane EM wave — they reach maxima and minima together. Option A confuses EM waves with AC circuits where V and I can be out of phase. Option C misapplies Lenz's law.
ELITE question · AIR under 50 level
This chapter has 131 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appEM Spectrum
Quick revision: most questions in this chapter test these facts.
| Wave | Key Fact |
|---|---|
| Radio waves | Longest λ; broadcasting, communication |
| Microwaves | Radar, microwave ovens, satellite communication |
| Infrared | Heat radiation; night vision; greenhouse effect |
| Visible light | VIBGYOR; only EM wave detected by human eye |
| Ultraviolet | Vitamin D synthesis; sterilisation; causes skin cancer |
| X-rays & Gamma | X-rays: medical imaging; Gamma: nuclear reactions, shortest λ, highest energy |
What the app covers in this chapter
399 questions in total, each with a detailed explanation.
| Grand Test | 75 |
| Mixed Revision | 55 |
| PYQ Mixed Concepts | 55 |
| Electromagnetic Spectrum | 40 |
| Radio Waves | 20 |
| Microwaves | 20 |
| Infrared Rays | 20 |
| Ultraviolet Rays | 20 |
| X-Rays | 20 |
| Gamma Rays | 19 |
| Electromagnetic Wave Applications | 19 |
| Nature of Electromagnetic Waves | 18 |
| Visible Light | 18 |
Questions students ask
Is Electromagnetic Waves important for NEET?
Moderately — 1 question usually appears. The EM spectrum order, uses of each type and properties of EM waves are commonly tested.
Which topics should I revise first?
Memorise the EM spectrum in order of increasing frequency, uses of each type, properties common to all EM waves (transverse, c = 3×10⁸ m/s), and Maxwell's displacement current concept.
How many questions from this chapter are on RankUp?
The RankUp app has 399 questions on Electromagnetic Waves, including 131 ELITE questions. Every question has a detailed explanation.
