An industrial photoelectric sensor uses a metallic cathode with work function
PHYSICS · Multi-part · A Level · Physics · Particles and radiation · Particles and radiation
Problem
An industrial photoelectric sensor uses a metallic cathode with work function 2.85eV. The manufacturer wishes to replace its current ultraviolet LED with a visible-light LED while maintaining reliable photoelectron emission.
(a) Calculate the minimum frequency of light required to cause electron emission from the cathode.
(b) Convert this frequency to the corresponding maximum permissible wavelength.
(c) Identify, by common color name, the region of the visible spectrum (e.g., red, orange, yellow, green, blue, violet) that satisfies the wavelength requirement you found.
(d) Provide one engineering advantage and one disadvantage of switching from ultraviolet to visible illumination in such a sensor, citing relevant physical considerations.