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If the speed of a charged particle moving perpendicular to a uniform magnetic field is doubled, its cyclotron frequency of revolution will:
ARemain unchanged
BBecome twice as large
CBecome half as large
DBecome four times as large
Answer & Solution
Correct answer: A. Remain unchanged
1. The cyclotron frequency is $\nu_c = \dfrac{qB}{2\pi m}$.
2. This expression contains only charge, field, and mass.
3. It does not contain the speed $v$, so changing $v$ does not change $\nu_c$.
4. Hence doubling the speed leaves the frequency unchanged; only the radius doubles.
_Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", p.139_
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