Question

FIGURE Q38.5 is the current-versus-potential-difference graph for a photoelectric-effect experiment with an unknown metal. If classical physics provided the correct description of the photoelectric effect, how would the graph look if:

a. The light was replaced by an equally intense light with a shorter wavelength? Draw it.

b. The metal was replaced by a different metal with a smaller work function? Draw it.

Short answer

a) Graph remains same.

b) x-intercept shifted towards left.

Step-by-step solution

Step 1.  It is given that we are assuming that classical physics provided the correct description of photoelectric effect.

We need to draw the graph if :

a) The light was replaced by an equally intense light with a shorter wavelength.

b) The metal was replaced by a different metal with a smaller work function.

And explain the reason for that type of graph.

Step 2. Part a) Plotting the graph along with the reason of this type of graph.

The graph will look like :

The reason for this type of graph is :

According to classical physics, The will be no effect on the wavelength of light. If the light intensity remains constant, the photocurrent will not vary. (the same amount of energy falls on the metal cathode).

Step 3. Part b) Plotting the graph along with the reason of this type of graph.

The graph will look like :

The reason for this type of graph is :

The electrons emitted from a cathode have a maximum kinetic energy of $K_{max}=E_{elec}-E_0$. If $E_0$is smaller for a different metal, The kinetic energy of the released electrons will be larger, resulting in a higher stopping potential.