Question

The photoelectric cut-off voltage in a certain experiment is 1.5 V. What is the maximum kinetic energy of photoelectrons emitted?

Answer 1

Hint: In this question, we will use the relation between the kinetic energy and the cut-off voltage. This equation will help us in getting the required result that is, the maximum energy of photoelectrons emitted in this experiment. Also, we will study about the basics of a photoelectric effect.

Formula used:
${K_e} = e{V_0}$

Complete step by step solution:
As we know that the cut-off voltage in an electrical circuit is known as the voltage at which a battery is considered fully discharged and beyond which further discharge could cause harm to the battery.
Here, the maximum kinetic energy of the emitted photoelectrons is given as:
${K_e} = e{V_0}$
Now, by substituting the given values in the above equation we get:
$\eqalign{
  & {K_e} = 1.6 \times {10^{ - 19}} \times 1.5 \cr
  & \therefore {K_e} = 2.4 \times {10^{ - 19}}J \cr} $
Therefore, we get the maximum kinetic energy of the photoelectrons emitted in the given experiment in the above result.

Additional information:
Kinetic energy of an object is the energy that it possesses due to motion of the object. It can be defined as the work needed to accelerate a body or object of given mass from rest to its velocity. When an object gains this energy during its acceleration, the object maintains this kinetic energy unless its speed or velocity changes.
When electrons are emitted when electromagnetic radiation, such as light, hits the material or its surface is called the photoelectric effect. The work function for photoelectric effect is different for different materials. It depends upon the intensity of light. The work function is the property of a material. It is defined as the minimum quantity of energy which is required to remove an electron to infinity from the surface of the material.

Note:
Total energy is given by the sum of potential energy and kinetic energy. Work function of a material is dependent on its kinetic energy. The unit of energy here is electron volt which is $1.602 \times {10^{ - 19}}Joule$ . The S.I unit of energy is Joule. At the maximum height the potential energy is maximum and kinetic energy is zero