Question

Identify which of the following light rays has the highest energy ?
A.) Violet
B.) Green
C.) Yellow
D.) Orange
E.) Red

Answer 1

Hint: The energy of the electromagnetic radiation is directly proportional to its frequency and inversely proportional to the wavelength. The wavelengths in VIBGYOR go on increasing as go from left to right.

Complete step by step solution:
Electromagnetic radiation is present all around us and is characterized by different wavelengths or frequencies. We have an electromagnetic spectrum categorizing various observed electromagnetic radiation. We can describe electromagnetic radiation either by their wavelength or their frequency.

The electromagnetic radiation consists of gamma rays, x-rays, ultraviolet rays, visible radiation, infrared radiation, microwaves and radio waves.
The frequency and wavelength are associated with each through the following relation.

$v = \dfrac{c}{\lambda }$

where $v$ is the frequency, $\lambda $ is the wavelength and c is the speed of light. Electromagnetic radiation travels with the speed of light $c = 3 \times {10^8}m{s^{ - 1}}$.
The relation energy of electromagnetic radiation was given by Einstein. According to him, energy of the electromagnetic radiation is directly proportional to the frequency of radiation.

$
  E \propto v \\
  E = hv = \dfrac{{hc}}{\lambda } \\
$

where h is called the Planck’s constant.

Using this relation we can calculate energy of electromagnetic radiation for different wavelengths.

The wavelengths of given colours are following:

Violet: 450nm
Green: 560nm
Yellow: 590nm
Orange: 635nm
Red: 700nm

Violet has minimum wavelength hence, has highest energy which is the required answer.

Note: This relation of energy holds only for electromagnetic radiations and wavelength increases as we go from gamma rays to radio waves with only visible radiation perceptible to our eye. Other waves like sound waves are not governed by this relation.