During the photoelectric effect, when photons strike with 5.1eV, electrons emitted from which metal have higher kinetic energy? Metal Na Ag Work function 2.3 eV 4.3 eV

Question

During the photoelectric effect, when photons strike with 5.1eV, electrons emitted from which metal have higher kinetic energy?

Metal

Answer 1

In the photoelectric effect, the kinetic energy of the emitted electrons depends on the energy of the incoming photons and the work function of the metal. The work function is the minimum energy required to release an electron from the surface of the metal. If the energy of the photon is greater than the work function, the excess energy is converted into the kinetic energy of the emitted electrons.

Given that the photon energy is 5.1 eV, let's consider a few examples of metals:

1. Sodium (Na): The work function of sodium is around 2.28 eV. When photons with 5.1 eV strike the sodium metal, the kinetic energy of the emitted electrons will be:

   $$K.E.=\text{Photon energy}-\text{Work function}=5.1\text{eV}-2.28\text{eV}=2.82\text{eV}$$

2. Copper (Cu): The work function of copper is around 4.7 eV. When photons with 5.1 eV strike copper, the kinetic energy of the emitted electrons will be:

   $$K.E.=5.1\text{eV}-4.7\text{eV}=0.4\text{eV}$$

As we can see from these examples, the kinetic energy of the emitted electrons is higher for sodium (2.82 eV) compared to copper (0.4 eV), even though the photon energy is the same in both cases.

Thus, sodium would have higher kinetic energy for the emitted electrons when photons with 5.1 eV strike the metal. The key factor is that the work function of sodium is lower than that of copper, allowing for more energy to be available for the kinetic energy of the emitted electrons.