Electromagnetic Waves for NEET UG
Light, radio, X-rays and microwaves are all the same kind of wave: oscillating electric and magnetic fields. Only the wavelength differs, and that decides how each one is used.
PhysicsClass 1256 MCQs2 lessons12 flashcards2 memory tricks
Practise Electromagnetic Waves free
What you'll learn
- What an electromagnetic wave is
Describe EM waves, their speed and the displacement current. - The electromagnetic spectrum and its uses
Order the EM spectrum by wavelength and match each band to its source and uses.
Key formulas
| Speed in vacuum | c = 1/√(μ₀ε₀) |
|---|---|
| Field amplitudes | E₀/B₀ = c |
| Displacement current | I_d = ε₀ dΦ_E/dt |
Memory tricks
Radio, Microwave, Infrared, Visible, Ultraviolet, X-ray, Gamma: frequency increases and wavelength decreases along the list.
Matching each band with an everyday use is a frequent NEET question.
Try 3 NEET-style questions
Q1. Which list is in order of increasing frequency?
- radio waves, microwaves, visible light, X-rays
- X-rays, visible light, microwaves, radio waves
- microwaves, radio waves, X-rays, visible light
- visible light, radio waves, microwaves, X-rays
Show answer
Answer: (1) radio waves, microwaves, visible light, X-rays
The spectrum in increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-rays, gamma rays.
Q2. In a plane electromagnetic wave, the average energy density is
- shared equally between the electric and magnetic fields
- carried mostly by the electric field component
- carried mostly by the magnetic field component
- carried only by the electric field, none by B
Show answer
Answer: (1) shared equally between the electric and magnetic fields
With B = E/c, the magnetic energy density B²/2μ₀ equals the electric energy density ε₀E²/2. The energy is shared equally.
Q3. Hertz produced electromagnetic waves experimentally using
- a photocell
- a spark-gap oscillator circuit
- a glass prism
- a diffraction grating
Show answer
Answer: (2) a spark-gap oscillator circuit
Hertz used an oscillating circuit with a spark gap to produce and detect radio waves, confirming Maxwell's theory.
Practise all 56 questions Free · explanations for every option · see where you go wrong