Electrons emitted with negligible speed from an electron gun are accelerated through a potential difference V along the x-axis. These electrons emerge from a narrow hole into a uniform magnetic field of strength B directed along x-axis. Some electrons emerging at slightly divergent angles as shown in the Fig. These paraxial electrons are refocused on the x-axis at a distance-
A
B
C
D
Text Solution
Verified by ExpertsThe correct answer is:
A
The electron will be refocused after travelling a distance 
pitch of helix
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