Arrange the following electromagnetic waves in the ascending order of their energies.
A. X-rays
B. UV-rays
C. Infrared rays
D. Microwaves
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → D, C, B, A
The energy of a photon is \( E = h\nu = hc/\lambda \), so energy increases as frequency increases (wavelength decreases). Typical wavelengths:
\( \text{Microwaves (D)}: 1\,\mathrm{mm}\text{ to }0.1\,\mathrm{m} \)
\( \text{Infrared (C)}: 700\,\mathrm{nm}\text{ to }1\,\mathrm{mm} \)
\( \text{UV rays (B)}: 1\,\mathrm{nm}\text{ to }400\,\mathrm{nm} \)
\( \text{X-rays (A)}: 10^{-3}\,\mathrm{nm}\text{ to }10\,\mathrm{nm} \)
Ascending order of energy: Microwaves < Infrared < UV < X-rays, that is, D, C, B, A.
NCERT (2026-27):
Summary – “… The spectrum of electromagnetic waves stretches, in principle, over an infinite range of wavelengths. Different regions are known by different names; γ-rays, X-rays, ultraviolet rays, visible rays, infrared rays, microwaves and radio waves in order of increasing wavelength from 10–2 Å or 10–12 m to 106 m.”