In the experimental study of photoelectric effect, a graph of stopping potential versus frequency of incident radiation for two metals A and B is plotted and identical slopes for both are obtained with different cut off frequencies $\left(v_{D B}>v_{O A}\right)$. So
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Slope for all metals is same = h/e. Here work function of B > work function of A
By Einstein’s photoelectric equation
$\phi=f_0+e V$
$h v=h v_0+e V$
$V=\frac{h v}{e}-\frac{h v_0}{e}$
On comparing with y = mx + x
$m=\frac{h}{e}$ for all metal
Cut-off frequency for B is more therefore work function of B will be more.