Question 7: If photoelectric effect is observed for some metal can you conclude that the effect will also be observed for another metal under the same conditions?

ANSWER

 A photon of energy E = hf when falls on the surface of a metal, it transfers this much energy to some electron of the metal and disappears itself. A part of this energy is used to eject the electron from the surface of the metal and the rest as the K.E of the electron. The minimum amount of energy required to eject an electron from the surface of the metal is called work function, denoted by φ.

Now different metals have different work functions. This means to eject an electron from their surfaces, different amount of energies are required for different metals. So if the conditions are same and the same photon is made incident on the surfaces of two metals, we should not expect the same effect in both cases of different metals.