Question

Miners in the family mine have discovered a new kind of metal alloy. You wish to find the work function of this alloy. How would you go about measuring it?

1. Using a light of known intensity, gather data on the kinetic energy of those electrons ejected from the metal
2. Using a light of known intensity, gather data on the rate at which electrons are ejected from the metal
3. Using a light of known frequency, gather data on the kinetic energy of those electrons ejected from the metal
4. Using a light of known frequency, gather data on the rate at which electrons are ejected from the metal

1, 2, 3, 4

3

2

3

2, 3, 4

1

2, 4

Answer 1

Work function of a metal alloy is defined as the minimum amount of energy required to knock out an electron from the outermost orbit of an alloy. Since work function deals with energy, therefore it has nothing to do with the intensity of light but only depends on the frequency of light.

According to photoelectric effect,

Incident energy= work function + kinetic energy.

Therefore, if the incident light has a greater energy than the work function then it is imparted as kinetic energy to the knocked out electron.

Also, we know that the incident energy of a light is given by = h × f , where h is the Planck's constant and f is the frequency of light used.

Hence to measure the work function of the metal alloy, we need to have a light of known frequency and gather the data on the kinetic energy of those electrons ejected from a metal.

Optoon 3 rd is correct.