An electron is moving in a circular path under the influence of a transverse magnetic field of 3.57×10^-2 T. If the value of e/m is 1.76×10^11 C/kg, the frequency of revolution of the electron is

1. 100 MHz

2. 62.8 MHz

3. 6.28 MHz

4. 1 GHz

Doubtly Asked 30 Oct 2026 NEET UG 2016 Phase 2 Practice test neet Save WhatsApp Report

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Answer: 4. 1 GHz

An electron in a magnetic field circles with frequency $f=\dfrac{eB}{2\pi m}=\dfrac{1}{2\pi}\cdot\dfrac em\cdot B$.

$$f=\frac{1.76\times10^{11}\times3.57\times10^{-2}}{2\times3.14}=\frac{6.28\times10^{9}}{6.28}\approx1\times10^{9}\ \text{Hz}$$

That is 1 GHz. Option (4). The frequency does not depend on speed or radius.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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