Photoelectric effect experiments are performed using three different metal plates $\mathrm{p}, \mathrm{q}$ and r having work functions $\phi_{p}=2.0 \mathrm{eV}, \phi_{q}=2.5 \mathrm{eV}$ and $\phi_{r}=3.0 \mathrm{eV}$, respectively. A light beam containing wavelengths of $550 \mathrm{~nm}, 450 \mathrm{~nm}$ and 350 nm with equal intensities illuminates each of the plates. The correct I-V graph for the experiment is [Take $h c=1240 \mathrm{eV} \mathrm{nm}$ ]

JEE Advanced · 2009 · 12 Apr 2009 · Paper 2 · Modern Physics

Photoelectric effect experiments are performed using three different metal plates

p, q

and r having work functions

ϕ_{p} = 2.0 eV, ϕ_{q} = 2.5 eV

and

ϕ_{r} = 3.0 eV

, respectively. A light beam containing wavelengths of

550 nm, 450 nm

and 350 nm with equal intensities illuminates each of the plates. The correct I-V graph for the experiment is
[Take

h c = 1240 eV nm

]

Answer: (A)

The stopping potential is given by

V_{0} = \frac{1}{e} [\frac{h c}{λ} - ϕ]

. For the three plates:

Since the intensities are equal, the photocurrent is proportional to the number of photons, which is proportional to wavelength. Thus

i_{p} : i_{q} : i_{r} = λ_{p} : λ_{q} : λ_{r} = 550 : 450 : 350

. Graph (A) correctly shows these stopping potentials and relative photocurrents.

JEE Advanced · 2009 · 12 Apr 2009 · Paper 2 · Single correct option