Case: Read the passage and answer the question.
The electromagnetic (EM) spectrum is the range of all types of EM radiation. Radiation is energy that travels and spreads out as it goes – the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation. The other types of EM radiation that make up the electromagnetic spectrum are microwaves, infrared light, ultraviolet rays, X-rays and gamma rays.
Consider the following statements about the radiations named in the passage:
(A) Infrared waves lie next to the long-wavelength end of the visible spectrum.
(B) Microwaves have longer wavelengths than radio waves.
(C) Visible light runs from about \(4\times10^{14}\) Hz to about \(7\times10^{14}\) Hz.
(D) Gamma rays lie in the upper frequency range of the electromagnetic spectrum.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A), (C) and (D) only
In order of decreasing wavelength, the spectrum runs from radio waves through microwaves, infrared, visible light, ultraviolet and X-rays to gamma rays. The frequency rises in the same order.
(A) Infrared waves lie next to the long-wavelength end of the visible spectrum. — True. Infrared comes just beyond red light. It has a longer wavelength and a lower frequency than visible light.
(B) Microwaves have longer wavelengths than radio waves. — False. Microwaves are short-wavelength radio waves. So their wavelengths are shorter than those of radio waves.
(C) Visible light runs from about \(4\times10^{14}\) Hz to about \(7\times10^{14}\) Hz. — True. This band of frequencies matches wavelengths of about 700 nm to 400 nm.
(D) Gamma rays lie in the upper frequency range of the electromagnetic spectrum. — True. Gamma rays have the highest frequencies and the shortest wavelengths of all the named radiations.
NCERT (2026-27):
Infrared waves – “Infrared waves are produced by hot bodies and molecules. This band lies adjacent to the low-frequency or long-wave length end of the visible spectrum. …”
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). …”
Visible rays – “It runs from about 4 × 1014 Hz to about 7 × 1014 Hz or a wavelength range of about 700 – 400 nm.”
Gamma rays – “They lie in the upper frequency range of the electromagnetic spectrum and have wavelengths of from about 10–10m to less than 10–14m.”