Question

For the photoelectric effect in sodium, the figure shows the plot of cut-off voltage versus frequency of incident radiation.
The threshold frequency is:

• A. $6.5\times {10}^{14}Hz$
• B. $4.5\times {10}^{14}Hz$
• C. $3\times {10}^{14}Hz$
• D. $5\times {10}^{14}Hz$

Answer 1

The correct option is C $3\times {10}^{14}Hz$

We know that threshold frequency is the minimum frequency of radiation that will produce photoelectric effect. Since for frequency below $3\times {10}^{14}Hz$, no current is observed, thus threshold frequency here is $3\times {10}^{14}Hz$