What is meant by the term angle of deviation? When it passes through a triangular glass prism why do different components of white light split up into a spectrum? Show how the red colour deviates from white light when it goes through a prism.

The angle of deviation is the angle formed between the direction of the incident ray (the original path of light) and the emergent ray (the path of light as it exits the prism). In simple terms, it is the measure of how much the light ray bends after passing through a prism. To define the angle of deviation: it shows the amount of bending experienced by a light ray due to refraction inside the prism.

Why White Light Splits into a Spectrum in a Prism

When a beam of white light enters a triangular glass prism, it undergoes refraction because light changes its speed as it moves from air into the denser medium (glass). Inside the prism, white light splits into its seven constituent colors: red, orange, yellow, green, blue, indigo, and violet. This splitting occurs because different colors of light travel at different speeds through the prism. As a result, they bend (or refract) by different amounts.

For example:

• Red light has the longest wavelength and travels faster through glass, so it bends the least.
• Violet light has the shortest wavelength and travels slower through glass, so it bends the most.

This variation in bending causes the light to fan out into a spectrum of colors, forming a rainbow-like pattern.

How Red Light Deviates Less

The red color deviates the least because it has the highest wavelength among the seven colors. The angle of deviation is smallest for red light because it bends the least when passing through the prism. On the other hand, violet light, with its shorter wavelength, has the largest angle of deviation. This difference in bending leads to the colors spreading out to form a spectrum.

To define the angle of deviation again: it is the angle between the incident ray and the emergent ray, showing how much the light bends inside the prism. The smaller the angle of deviation, the less the light bends. This is why red light, with its high wavelength, shows the smallest deviation among the colors of white light.

By understanding this concept, we can explain why prisms create rainbows and how light interacts with different materials.