Question

Which color of light has the greatest energy per photon?
A. Blue
B. Green
C. Violet
D. Red

Answer 1

Hint: Light is considered to be made up of massless particles travelling at the speed of light. To figure out which colour of light has the greatest energy per photon use the formula of energy of a photon i.e.$E=h\nu$. The violet light has the greatest frequency.

Formula used:
 $E=h\nu$

Complete step by step answer:
It is considered that light has dual nature. This means that light acts as a particle as well as a wave. The particle nature of light is proved by the photoelectric theory. The wave nature of light is proved in several phenomena such as interference, refraction and reflection of light using Huygens's principle.
If we consider light as a particle, we say that light is made of massless particles. These massless particles are called photons. The photons of the light travel with the speed of light in the respective medium. In vacuum, the speed of each photon is equal to $3\times {10}^{8}m{s}^{-1}$.
The photons are said to be energy packages. Therefore, we say that light consists of some energy. The energy of a photon is equal to $E=h\nu$.
Here h is the Planck’s constant and $\nu$ is the frequency of the light.
Now, we know that light is a collection of waves of several frequencies. Each light with particular frequency has a particular colour to the light. Therefore, light with different colour has different energy per photon (i.e. energy of one photon).
If we follow the spectrum of light, we get to know that violet has the greatest frequency. Since the energy of a photon is directly proportional to the frequency of the light, the light having the greatest frequency will have the greatest energy per photon.
Therefore, the violet light will have the greatest energy per photon.
Hence, the correct option is C.

Note:
We can also related the energy per photon by the wavelength of the light by using the formula $\nu ={\displaystyle \frac{c}{\lambda }}$, c is the speed of the light in vacuum and $\lambda$ is the wavelength of the light. Then we can use the energy of the photon as $E={\displaystyle \frac{hc}{\lambda }}$. Therefore, the light having the least wavelength will have the greatest energy and violet light has the least wavelength.