Identify the electromagnetic waves based on their application from the statements given below, and arrange them in ascending order of their wavelength.
(A) Used in the remote switch of TV set.
(B) Suitable for radar systems used in aircraft navigation.
(C) Used to kill germs in water purifier.
(D) Suitable for destroying cancer cells.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (D), (C), (A), (B)
Each application points to one band of the electromagnetic spectrum:
(A) Used in the remote switch of TV set. — infrared
(B) Suitable for radar systems used in aircraft navigation. — microwaves
(C) Used to kill germs in water purifier. — ultraviolet
(D) Suitable for destroying cancer cells. — gamma rays
In order of increasing wavelength the spectrum runs: gamma rays, X-rays, ultraviolet, visible, infrared, microwaves, radio waves.
So the ascending order of wavelength is (D), (C), (A), (B).
NCERT (2026-27):
Electromagnetic Spectrum – “… We briefly describe these different types of electromagnetic waves, in order of decreasing wavelengths.”
Microwaves – “… Due to their short wavelengths, they are suitable for the radar systems used in aircraft navigation.”
Infrared Waves – “… Electronic devices (for example semiconductor light emitting diodes) also emit infrared and are widely used in the remote switches of household electronic systems such as TV sets, video recorders and hi-fi systems.”
Ultraviolet Rays – “… UV lamps are used to kill germs in water purifiers.”
Gamma Rays – “… They are used in medicine to destroy cancer cells.”