Choose the correct option relating wave lengths of different parts of electromagnetic wave spectrum:

Solution

Physics sir · 3 steps

Line up the spectrum from longest to shortest wavelength, then check each option against that one order.

1. The spectrum order. In order of decreasing wavelength the spectrum runs: radio waves, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays. Frequency rises in the same direction, since c = fλ is fixed.

   Region	Typical wavelength
   Radio waves	above about 0.1 m
   Microwaves	about 1 mm to 0.1 m
   Visible	about 400 nm to 700 nm
   X-rays	about 10⁻³ nm to 10 nm

2. Check the options. Only (a) follows this order: λ_(radio) > λ_(micro) > λ_(visible) > λ_(X-ray). Options (b), (c) and (d) each place either visible light or X-rays above radio waves, which is wrong.
3. So. The correct relation is option (a).

The idea to keep. Remember the spectrum as one fixed line: radio, micro, IR, visible, UV, X, gamma. Wavelength falls and frequency and photon energy rise as you move along it.

Answer from the NTA final answer key. Solution by PrepWiser.