CBSE 2025 · Region 7 · Set 2 · Q25 · 3 marks
(a)How are electromagnetic waves produced ?(b)Write the wavelength range and one use of :(i)Microwaves, and(ii)Ultraviolet waves.
(a)
How are electromagnetic waves produced ?
(b)
Write the wavelength range and one use of :
(i)
Microwaves, and
(ii)
Ultraviolet waves.
Marking-scheme solution
(a)
Electromagnetic waves are produced by an oscillating (accelerated) charge: it sets up oscillating electric and magnetic fields which regenerate each other and propagate through space as an EM wave.
(i)
Microwaves — wavelength range ~$\displaystyle 0.1$ m to $\displaystyle 1$ mm; use: RADAR / microwave ovens.
(ii)
Ultraviolet waves — wavelength range ~$\displaystyle 4$×$\displaystyle 10$⁻⁷ m ($\displaystyle 400$ nm) to ~$\displaystyle 6$×$\displaystyle 10$⁻¹⁰ m; use: sterilisation of water / LASIK eye surgery / detecting forged bank notes.
Electromagnetic WavesRemembershort_answereasy
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.