When the frequency of a photon is below the threshold frequency for a given material, the electrons in the material do not have enough energy to overcome the binding energy that holds them in place. As a result, the electrons remain in their original energy states and no electrons are emitted from the material.

Therefore, no electric current or photoelectric effect is observed when the photon frequency is below the threshold frequency. The threshold frequency is a characteristic property of each material and it determines the minimum energy required to emit electrons from that material.