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Question
Define the term "Threshold frequency", in the context of photoelectric emission.
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Solution
For a given Photosensitive material, there is a certain minimum cut off frequency at which Photoelectric emission is possible is called Threshold frequency, i.e. At this frequency just emission of photoelectrons happens without giving them any kind of additional energy. Higher the work function of the material, greater is the Threshold frequency. See the figure below of two different metals having different Threshold Frequency.
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