Q118 / 180 · AIIMS 2017 · Physics

Assertion : As work function of a material increases by some mechanism, it requires greater energy to excite the electrons from its surface. Reason : A plot of stopping potential $\left(V_s\right)$ versus frequency (v) for different metals, has greater slope for metals with greater work functions.

A
If both assertion and reason are true and reason is the correct explanation of assertion.
B
If both assertion and reason are true but reason is not the correct explanation of assertion.
Correct answer
C
If assertion is true but reason is false.
D
If both assertion and reason are false.

Solution

As eV $=h \mathrm{~s}-W$ $V_{\mathrm{s}}=\left(\frac{h}{e}\right) \mathrm{v}-\left(\frac{W}{e}\right)$ For $V_{\mathrm{s}}$ versus $v$ graph, slope $=\frac{h}{e}=$ constant.

Hence, the correct answer is option: 'C'.

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