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Physics · 2025 · 3 marks
CBSE 2025 · Region 2 · Set 2 · Q25
(a) How is an electromagnetic wave produced? (b) An electromagnetic wave is travelling in vertically upward direction. At an instant, its electric…
(a)
How is an electromagnetic wave produced?
(b)
An electromagnetic wave is travelling in vertically upward direction. At an instant, its electric field vector points in west direction. In which direction does the magnetic field vector point at that instant?
(c)
Estimate the ratio of shortest wave length of radio waves to the longest wave length of gamma waves.
Marking-scheme solution
(a)
Electromagnetic waves are produced by accelerating / oscillating charges.
(b)
South direction
(c)
$\displaystyle \frac{\text { Shortest wavelength of radio waves }}{\text { Longest wavelength of gamma waves }}=\frac{0.1}{10^{-12}}=10^{11}$
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CBSE Class 12 Physics past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.