In electromagnetic spectrum, \( \nu_1 \), \( \nu_2 \) and \( \nu_3 \) respectively denote the frequencies of microwaves, ultraviolet waves and gamma-rays. We can conclude that :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( \nu_1 \lt \nu_2 \lt \nu_3 \)
In the electromagnetic spectrum the frequency increases in the order radio waves, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays.
Microwaves lie at the low-frequency end, ultraviolet in the middle and gamma rays at the highest frequencies:
\( \nu_1 \sim 10^{9}\text{ to }10^{11}\,\mathrm{Hz} \)
\( \nu_2 \sim 10^{15}\text{ to }10^{17}\,\mathrm{Hz} \)
\( \nu_3 \gt 10^{19}\,\mathrm{Hz} \)
So \( \nu_1 \lt \nu_2 \lt \nu_3 \).
NCERT (2026-27):
Electromagnetic Spectrum – “… The classification of em waves according to frequency is the electromagnetic spectrum (Fig. 8.4). … We briefly describe these different types of electromagnetic waves, in order of decreasing wavelengths.”
Microwaves – “Microwaves (short-wavelength radio waves), with frequencies in the gigahertz (GHz) range, are produced by special vacuum tubes (called klystrons, magnetrons and Gunn diodes).”
Gamma Rays – “They lie in the upper frequency range of the electromagnetic spectrum and have wavelengths of from about 10–10 m to less than 10–14 m.”