Chapter U5, Problem 15RE

Interpretation Introduction

Interpretation:

The ray model, wave model and photon model of light needs to be explained. The sketch for each model also needs to be drawn showing transmission through a thin red film of plastic.

Concept introduction:

The optical phenomena can be explained with the help of three important models. These are based on three different ways of describing the electromagnetic radiation. This includes rays, ways and photons.

Explanation of Solution

A ray model of light represents light as a ray travelling in the straight path. The direction of this ray can be changed when obstacles is placed in its path otherwise it always travel in straight path.

The ray model of the light is represented as follows:

Ray model of light

The reflected ray is the light ray which gets reflect by the surface of medium during transmission. Here, refracted ray is the ray which transmitted to the second medium and the direction will be different from the incident ray.

The wave model of light explains that light travels as a wave. According to this model, when a wave is passed through an opening, it spreads out. The spreading of wave depends on its wavelength. The short wavelength waves spread out little but long wavelength waves spread out more.

Wave model of light

In the above wave model, wavelength is the distance between two consecutive crest or trough, frequency in the number of times a wave passes through a point in 1 second, amplitude is the height of crest or trough in a wave or it is the maximum distance moved by a point in the vibrating body.

It does not explain the photoelectric effect which is observed when light is focused on metal and it emits electrons. In this case, the frequency is directly proportional to the energy thus; light with higher frequency has higher energy. All this is explained by photon model of the light.

Photon model of light

According to Einstein, light travels in the form of discrete packets known as photons with energy.

Here,

$E_{photon}=h\nu$

Where, h is Planck’s constant and $\nu$ is frequency of light.