Suppose that, in a photoelectric effect experiment of the type described above, light, with a wavelength of 400 nm results in a voltage reading of 0.8 V.

(a) What is the work function for this photocathode?

(b) What voltage reading would you expect to obtain if the wavelength were changed to 300 nm? What if the wavelength were changed to 500 nm? 600 nm?

Solution 2P

The relationship between voltage, energy of photons and work function is given as

Here, is the wavelength of light and is the work function of the photocathode.

(a)

Step 1

Given, wavelength of light

Voltage

We have to calculate .

Substituting these values in equation (1),

Therefore, the work function of the photocathode is .

(b) The work function

Step 1

Wavelength

From equation (1),

Therefore, the voltage reading corresponding to the wavelength is 1.83 V.