CBSE Class 12 · 2008 · All India · EM WavesVery Short Answer

The frequency of oscillation of the electric field vector of a certain electromagnetic wave is

5 \times 1 0^{14}

Hz. What is the frequency of oscillation of the corresponding magnetic field vector, and to which part of the electromagnetic spectrum does it belong?

Answer: Same frequency, $5 \times 1 0^{14}$ Hz; it lies in the visible region.

Solution

In an electromagnetic wave the electric and magnetic field vectors oscillate in phase and with exactly the same frequency.
Hence the magnetic field also oscillates at

5 \times 1 0^{14}

Hz.
This frequency corresponds to a wavelength

λ = c / f \approx (3 \times 1 0^{8}) / (5 \times 1 0^{14}) \approx 6 \times 1 0^{- 7}

= 600

nm, which lies in the visible part of the spectrum.

f_{B} = 5 \times 1 0^{14} Hz, visible light

CBSE Class 12 Board · 2008 · All India · Subjective

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