Question
The threshold frequency for a metal is . Light of frequency falls on the metal. What will be the cutoff voltage for photoelectric emission.

2.0 V

2.5 V

1.0 V

None of these
easy
Solution
2.0 V
If v be the frequency of light falling on the metal and v_{0} the threshold frequency, then by photoelectric equation, the maximum kinetic energy of the emitted photoelectrons is given by
Also, if V_{0} be the cutoff voltage, then
From these two equations, we have
= 2.0 V.
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