Question

Is threshold a frequency?

Answer 1

The threshold frequency:

1. A minimal frequency below which, regardless of the strength of the incident radiation, photoelectric emission is not achievable.
2. A frequency is a threshold. It is described as the lowest frequency needed for a radiation incident to produce a photoelectric emission.
3. Photoemission is the term used to describe the process by which photoelectrons are emitted from the metal surface as a result of light.

Hence, the threshold is the lowest frequency needed for a radiation incident to produce a photoelectric emission.