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 ▸An electrical heater supplies 500J of heat energy to a copper cylinder of mass 32.4g Find the increase in temperature of the cylinder. (Specific heat capacity of copper = 385 J*kg^-1*Celsius^-1
A man weighing 600N steps on a scale that contains a spring. The spring is compressed 1cm under their weight. Find the force constant of the spring and total work done on its compression.
A stone is thrown horizontally at 5m/s from a platform 10m above ground. Find time till impact with ground.
State Newton's Law of Gravitation