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(C) The photoelectric current $I$ is directly proportional to the number of photoelectrons emitted per second,which in turn is proportional to the num

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(C) The photoelectric current $I$ is directly proportional to the number of photoelectrons emitted per second,which in turn is proportional to the number of incident photons per second.If the power $P$ of the incident light is kept constant,then $P = n \cdot \frac{hc}{\lambda}$,where $n$ is the number of photons incident per second.Thus,$n = \frac{P \lambda}{hc}$.Since $I \propto n$,we have $I \propto \lambda$.However,the photoelectric effect only occurs if the wavelength $\lambda$ is less than or equal to the threshold wavelength $\lambda_0$ (i.e.,$\lambda \le \lambda_0$).As $\lambda$ increases from a small value towards $\lambda_0$,the number of photons $n$ required to maintain constant power $P$ increases,and thus the photoelectric current $I$ increases linearly with $\lambda$ until $\lambda = \lambda_0$,beyond which the current drops to zero. This behavior is represented by graph $C$.

List-$I$	List-$II$
$a$. Franck-Hertz Experiment	$i$. Particle nature of light
$b$. Photo-electric Experiment	$ii$. Discrete energy levels of atom
$c$. Davisson-Germer Experiment	$iii$. Wave nature of electron
	$iv$. Structure of atom

$List-I$	$List-II$
$A$. Michelson-Morley experiment	$I$. The existence of anti-matter
$B$. Stern-Gerlach experiment	$II$. The existence of de-Broglie matter waves
$C$. Davisson-Germer experiment	$III$. Electrons have spins
$D$. Anderson discovery of positron	$IV$. The non-existence of ether

The anode voltage of a photocell is kept constant. The wavelength of the incident light on the cathode is changed gradually. Then,the photoelectric current $I$ of the photocell varies according to which of the following graphs?

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