A metallic surface of area is irradiated by a monochromatic beam of wavelength…
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
A metallic surface of area 0.50cm2 is irradiated by a monochromatic beam of wavelength 400nm carrying an incident power of 5.0mW. The surface emits one electron for every 50 photons incident (quantum efficiency 2%).
(i) Calculate the number of photons incident per second on the surface.
(ii) Determine the saturation photocurrent generated under these conditions.
(iii) If the incident power is reduced to 1.0mW, find the new saturation current. State what happens to the stopping potential when the power is reduced, giving a brief reason.