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In Thomson's method of determining e/m o...

In Thomson's method of determining e/m of cathode rays, magnetic field (B) and electric field ( E) are parallel a parabola is not. Obtained on the screen. The reason is _______ .

A

Cathode rays consist of electrons which carry negative charge

B

Electron is very light particle

C

There is no velocity distribution in cathode rays

D

Parallel fields B and E do not interact with electrons

Text Solution

Verified by Experts

The correct Answer is:
C
In case of positive rays we get a parabola when B and E are parallel because different positive ions have different velocities and they reach at different points on the parabola. If the velocities of all the ions be the same, only a point will be obtained on the screen. Since there is no velocity - distribution in cathode rays , hence no parabola is obtained.
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