Question

The correct graph representing the relation between energy (E) of photoelectrons and frequency (v) of incident light is

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

Key Idea: Photoelectric equation has same form as equation of straight line. If using light of different frequencies a graph is plotted between the maximum kinetic energy $E_k$ of the photoelectrons and frequency (v) of light, then a straight line is obtained, according to relation $E_k=h{v}_0-W,$ where W is the intercept cut by straight line on negative $E_k-$ axis.
Note: If the straight line is extended backwords, it intersects the frequency axis at a point $v_0$ and intercepts the energy axis at - w. This means that for the photoelectrons to be emitted from a given metal plate the frequency of incident light should be higher than $v_0,$ otherwise no photoelectrons are emitted.