When red light is shone on a metal, regardless of the intensity of this light, no current will flow. However if blue light is shone on this metal a current will flow. Why does this occur?
This problem can be solved by first considering the energy of a photon e = hf. A photon of red light lacks the sufficient energy to free an electron. However a photon of blue light has a higher frequency and thus has a higher energy. This allows for a photon of blue light to free an electron and thus allow for a current to flow when a large number of photons are sent towards the metal.
JP
Related Physics A Level answers
All answers ▸What velocity should your boat have if you want to cross a 72m wide river in 6s by the shortest distance, with a 5 m/s downstream current?
The roar of a tiger in a zoo can be heard by visitors at the entrance, even though the tiger can not be seen because there is a hill in the way. Name and explain this effect.
A block of mass (m) is placed on a rough slope inclined at an angle (a) to the horizontal, find an expression in terms of (a) for the smallest coefficient of friction (x), such that the block does not fall down the slope.
How do you find the components of a vector?