Arrange the wavelengths of the following radiations in the decreasing order:
\( \lambda_{\text{visible}},\ \lambda_{\text{X-rays}},\ \lambda_{\text{radiowaves}},\ \lambda_{\gamma\text{-rays}} \)
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → \( \lambda_{\text{radiowaves}} \gt \lambda_{\text{visible}} \gt \lambda_{\text{X-rays}} \gt \lambda_{\gamma\text{-rays}} \)
In the electromagnetic spectrum the wavelength decreases as the frequency increases. The approximate wavelength ranges are
Radio waves: more than 0.1 m
Visible light: about 400 nm to 700 nm
X-rays: about 1 nm to \( 10^{-3} \) nm
Gamma rays: less than \( 10^{-3} \) nm
Arranging them from the longest wavelength to the shortest:
\( \displaystyle \lambda_{\text{radiowaves}} \gt \lambda_{\text{visible}} \gt \lambda_{\text{X-rays}} \gt \lambda_{\gamma\text{-rays}} \)
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.”