1. Tardigrade
  2. Question
  3. Physics
  4. 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 t =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 )

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Q. Photoelectric effect experiments are performed using three different metal plates $p , q$ and $r$ having work functions $\phi_{ p }=2.0 \,eV , \phi_{ q }=2.5\, eV$ and $\phi_{ t }=3.0 \,eV$, 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 $h c=1240\, eV\, nm$ )

JEE AdvancedJEE Advanced 2009

Solution:

$ V _{ B }=(1 / e )[( hc / \lambda)-\phi]$
$ V _{ P }=(1 / e )[(1240 / 550)-2] eV =0.2545 V $
$V _{ q }=(1 / e )[(1240 / 450)-2.5] eV =0.255 V $
$ V _{ r }=(1 / e )[(1240 / 350)-3] eV =0.5428 V$
If $n$ is the number of photons in unit time then $nh c / \lambda = I$
$\Rightarrow i _{ p }: i _{ q }: i _{ r }= n _{ P }: n _{ q }: n _{ r }=\lambda_{ p }: \lambda_{ q }: \lambda_{ r }$