Electromagnetic Waves MCQs Class 12 Physics
Electromagnetic Waves MCQs Class 12 Physics
Class: 12 | Subject: Physics
Section: 5 – Electromagnetic Waves
Topic: Electromagnetic Waves MCQs
Based on: CBSE Board Examination Pattern
Section: 5 – Electromagnetic Waves
Topic: Electromagnetic Waves MCQs
Based on: CBSE Board Examination Pattern
Instructions: These Multiple Choice Questions (MCQs) are designed strictly as per the NCERT syllabus, making them ideal for CBSE Class 12 Board Examination preparation.
1. Electromagnetic waves are:
Answer: B
EM waves are transverse because electric and magnetic fields oscillate perpendicular to each other and to the direction of propagation.
EM waves are transverse because electric and magnetic fields oscillate perpendicular to each other and to the direction of propagation.
2. Speed of electromagnetic waves in vacuum is:
Answer: D
Speed = 3 × 10⁸ m/s = 3 × 10⁵ km/s. It is determined by ε₀ and μ₀.
Speed = 3 × 10⁸ m/s = 3 × 10⁵ km/s. It is determined by ε₀ and μ₀.
3. Ratio of electric to magnetic field in EM waves gives:
Answer: C
E/B = c, the speed of light.
E/B = c, the speed of light.
4. Which EM wave has highest frequency?
Answer: B
Gamma rays occupy the highest frequency region of EM spectrum.
Gamma rays occupy the highest frequency region of EM spectrum.
5. Microwaves are used in:
Answer: D
Microwaves penetrate atmosphere easily and heat water molecules → used in ovens, radar, satellites.
Microwaves penetrate atmosphere easily and heat water molecules → used in ovens, radar, satellites.
6. Infrared waves are emitted by:
Answer: A
All hot objects emit IR radiation due to thermal motion.
All hot objects emit IR radiation due to thermal motion.
7. Visible light wavelength range is approximately:
Answer: B
Visible spectrum spans ~400 nm (violet) to 700 nm (red).
Visible spectrum spans ~400 nm (violet) to 700 nm (red).
8. UV rays are used for:
Answer: A
UV kills bacteria → used in water purification and sterilization.
UV kills bacteria → used in water purification and sterilization.
9. X-rays are produced when:
Answer: A
High-speed electrons decelerate → Bremsstrahlung radiation.
High-speed electrons decelerate → Bremsstrahlung radiation.
10. EM waves do not require:
Answer: C
They propagate through vacuum.
They propagate through vacuum.
11. Order of increasing wavelength:
Answer: A
Standard EM spectrum order.
Standard EM spectrum order.
12. Energy of EM wave depends on:
Answer: A
E = hν → directly proportional to frequency.
E = hν → directly proportional to frequency.
13. Radio waves are used in:
Answer: A
Due to long wavelength → good diffraction → long-distance transmission.
Due to long wavelength → good diffraction → long-distance transmission.
14. Maxwell predicted EM waves using:
Answer: C
From changing electric & magnetic fields.
From changing electric & magnetic fields.
15. First to verify EM waves experimentally:
Answer: B
He generated and detected radio waves.
He generated and detected radio waves.
16. Magnetic field in EM wave is:
Answer: B
E ⟂ B ⟂ direction of propagation.
E ⟂ B ⟂ direction of propagation.
17. EM waves carry:
Answer: C
Radiation pressure proves momentum transfer.
Radiation pressure proves momentum transfer.
18. Heating effect maximum in:
Answer: A
Infrared strongly absorbed as heat.
Infrared strongly absorbed as heat.
19. EM waves are produced by:
Answer: B
Acceleration causes changing fields → radiation.
Acceleration causes changing fields → radiation.
20. Displacement current concept was given by:
Answer: A
It completed Ampere’s law and led to EM wave prediction.
It completed Ampere’s law and led to EM wave prediction.