Short Answer

A prism splits white light because different colors in white light bend by different amounts when they pass through the prism. This bending of light is called refraction. Each color has a different wavelength, so each color slows down differently inside the prism and bends differently.

As a result, the colors spread out into a beautiful band called the spectrum. This is why white light separates into seven colors—violet to red—when it passes through a glass prism.

Detailed Explanation :

Why a Prism Splits White Light

A prism splits white light because of a process called dispersion, which occurs when light enters a medium where different wavelengths bend differently. White light is not a single color; it is a combination of many colors, and each color behaves in its own way when passing through glass. When white light enters a prism, the colors separate due to varying degrees of refraction.

This phenomenon explains the formation of rainbows, color patterns, and many optical effects in nature. Understanding how a prism splits white light helps us learn about the nature of light, wavelengths, and color formation.

1. Nature of White Light

White light is made of seven main colors:
Violet, Indigo, Blue, Green, Yellow, Orange, and Red (VIBGYOR).

Each color has:

• Different wavelength
• Different speed in a medium
• Different degree of bending

This difference becomes clear when white light passes through a prism.

2. Refraction of Light in a Prism

Refraction occurs when light passes from one medium to another and changes speed.
A prism has two sloping surfaces, and light bends twice:

1. When entering the prism
2. When leaving the prism

Because of its shape, a prism bends light more than a flat glass slab.

When white light enters the prism:

• It slows down
• It bends toward the normal

When it exits:

• It speeds up
• It bends away from the normal

But each color bends differently.

3. Dispersion – The Main Reason

Dispersion is the separation of white light into its component colors.
This happens because:

• Each color has a different wavelength
• Each wavelength bends by a different amount

Colors with shorter wavelength bend more.
Colors with longer wavelength bend less.

Order of bending:

• Violet (most)
• Indigo
• Blue
• Green
• Yellow
• Orange
• Red (least)

This bending causes the colors to spread out and form a spectrum.

4. Why Do Colors Bend Differently?

The key reason is different speeds of different wavelengths in glass.

• Violet light has a short wavelength → travels slowest → bends the most
• Red light has a long wavelength → travels fastest → bends the least

This difference makes each color follow a slightly different path inside the prism.

5. Shape of the Prism Helps Splitting

A prism has a triangular shape, not flat like a glass slab.
Because of this shape:

• Rays enter at an angle
• Rays exit at another angle
• Refraction happens twice
• Separation becomes clear

Thus, the geometry of the prism enhances dispersion.

6. Formation of Spectrum

When the separated colors come out of the prism, they spread out on a screen or surface, forming a spectrum.

This spectrum ranges from violet (high energy) to red (low energy).
This spectrum is what we see in:

• Rainbows
• Glass prisms
• Crystal decorations
• CD surfaces

The spectrum is proof that white light contains many colors.

7. Everyday Examples of Dispersion

Infrared and ultraviolet are outside the visible range, but VIBGYOR colors show how dispersion works.

Common examples:

• A rainbow after rainfall
• Color patterns in soap bubbles
• Colors on oil films
• Light passing through water drops
• Crystal and diamond sparkle

All these effects are due to light spreading into different colors.

8. Importance of Dispersion

Dispersion is important in science and technology:

• Spectroscopy to study materials
• Creation of rainbows
• Lens and optical device design
• Colour photography and printing
• Fiber optic communication uses controlled dispersion

Understanding dispersion helps scientists analyze light from stars, planets, and galaxies.

Conclusion

A prism splits white light because different colors in white light bend by different amounts when they pass through the prism. This separation of colors, called dispersion, occurs because each color has a different wavelength and speed in glass. Violet bends the most, and red bends the least, creating the visible spectrum. The prism’s triangular shape helps spread the colors apart. Thus, the splitting of white light reveals the true nature of light as a combination of many colors.