Question

A laser beam of pulse power ${10^{12}}W$ is focused on an object of area ${10^{ - 4}}c{m^2}$. The energy flux in $W/c{m^2}$ at the point of focus is
A) ${10^4}$
B) ${10^8}$
C) ${10^{16}}$
D) ${10^{20}}$

Answer 1

Hint: Laser is a form of radiant energy. The full form of LASER is ‘ Light Amplification By the Stimulated Emission of Radiation’. A laser is a device that produces a narrow beam of radiation by stimulating atoms or molecules. A laser beam can be focused on an area equal to the square of its wavelength.

Complete step by step answer:
The term ‘flux’ means to change or fluctuate. Energy flux is a quantity that is defined as the rate of energy transfer through any given area. The pulse power supply is a device that produces very high power and accumulates energy.

Given that pulse power $ = {10^{12}}$
Area $ = {10^{ - 4}}$
Energy flux is given by
$\Phi = \dfrac{{\text{Pulse Power}}}{\text{{Area}}}$
Substituting the values and solving,
$\Rightarrow \Phi = \dfrac{{{{10}^{12}}}}{{{{10}^{ - 4}}}}$
$\Rightarrow \Phi = {10^{16}}Watt/c{m^2}$

Therefore, the energy flux at the point of focus of the laser beam will be ${10^{16}}Watt/c{m^2}$. Hence Option (C) is the right answer.

Note:
The principle of laser emission was first observed and developed by Einstein in 1917. As per its principle, the atoms or molecules have a specific amount of energy stored in them depending on their nature. Lasers make a high-intensity directional beam that has a very narrow frequency. Lasers are mostly used as a strong electromagnetic beam. There are different types of lasers out of which some are used for cutting materials and others are used as a presentation of light. It is to be noted that the laser beam is different from an ordinary beam of light. This is because the laser beam is highly directional but ordinary light is not monochromatic.