Question

In a series of photoelectric emission experiments on a certain metal surface, possible relationships between the following quantities were investigated: threshold frequency $f_0$, frequency of incident light f, light intensity P, photocurrent I, maximum kinetic energy of photoelectrons $T_{max}$. Two of these quantities, when plotted as a graph of y against x, give a straight line through the origin. Which of the following correctly identifies x and y with the photoelectric quantities?

• A. x- I, y-$f_o$
• B. x- f, y-$f_o$
• C. x- P, y-I
• D. x-P, y-$T_{max}$

Answer 1

Answer: (C)

x- P, y-I

Out of the given quantities $P,I,f_0,T_{max}$ . We know that only $P$ and $I$ have a linear dependence. i.e on increasing the light intensity $P$, the no. of photoelectrons per second increases by the same amount. So, the graph of $P$ as an independent variable i.e. x and $I$. as the dependent variable i.e. y, is a straight line.