Question

1. A laser emits photons with frequency of 850 THz. Which of the following materials are suitable to be used with the laser to produce free electrons?

Table 1: Various Elements and their Work Functions

Material	Work Function (10-19 Joules)
Lithium	4.646
Arsenic	6.008
Potassium	3.669
Calcium	4.598
Cadmium	6.537

Answer 1

Here,the free electrons from the atom of the element will emit if and only if the energy of the photon is larger than that of the work function of the element.

Here,the frequency of the emitted photon by laser,

So,the energy of photon,

From the work functions of the elements given below,the elements with work function less than the energy of photon are,

Lithium, Potassium and Calcium.

So,the laser of this energy can produce electron for the following materials,

Lithium, Potassium and Calcium.