Question

Photoelectric effect experiments are performed using three different metal plates $p, q$ and $r$ having work functions $Q_{s}=2.0\, eV , Q_{q}=2.5\, eV$ and $Q_{r}=3.0 eV$, are respectively. A light beam containing wavelength 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 $h_{c}=1240 \,eV nm$ )

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

$E_{\lambda_{1}}=550\, nm =\frac{1240}{550} eV =2.25\, eV$
$E_{\lambda_{2}}=450 \,nm =\frac{1240}{450} eV =2.8\, eV$
$E_{\lambda_{3}}=350 \,nm =\frac{1240}{350} eV =3.5 \,eV$
From plate $p$, electrons are ejected by wavelengths $550 , 450$ and $350\, nm$.
From plate $q$, electrons are ejected by wavelengths $450$ and $350 \,nm$.
From plate $r$, electrons are ejected by wavelength $350 \,$.