Dispersion of white light is a fascinating optical phenomenon that occurs when light is refracted through a prism. A prism is typically made of glass and has a specific geometric shape, usually a triangular cross-section, which plays a crucial role in separating light into its constituent colors.

Understanding White Light

White light, such as sunlight, is composed of a mixture of different colors, each with a unique wavelength. These colors include:

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

Together, these colors form the spectrum of light, often remembered by the acronym "VIBGYOR."

Mechanism of Dispersion

The process of dispersion occurs when white light enters a prism. The mechanism can be understood through the following steps:

• Entry of Light: When white light strikes the surface of the prism, it enters a denser medium (glass) from a less dense medium (air). This change in density causes the light to refract, or bend, towards the normal line.
• Separation of Colors: Different colors of light refract at different angles due to their varying wavelengths. Shorter wavelengths (e.g., blue and violet) are refracted more than longer wavelengths (e.g., red). This leads to the separation of colors.
• Exiting the Prism: As the refracted light exits the prism back into the air, it bends away from the normal. The angles of refraction for each color cause them to spread out further, forming a spectrum.

Observation of the Spectrum

The spectrum created by the dispersion of light can be observed as follows:

• Positioning the Prism: To observe the spectrum, place the prism in the path of a beam of white light, such as sunlight or light from a projector.
• Formation of Spectrum: A colorful band of light, displaying the colors of the rainbow, will emerge on the opposite side of the prism. The order of colors from top to bottom is: violet, indigo, blue, green, yellow, orange, and red.

Angle of Deviation

The angle of deviation (D) is an important concept in understanding dispersion. It is defined as the angle between the incident ray and the emergent ray. The angle of deviation varies with the wavelength of light:

• For Violet Light: It experiences the greatest angle of deviation.
• For Red Light: It experiences the least angle of deviation.

This variation in deviation is what causes the colors to spread out and form a distinct spectrum.

Applications of Dispersion

The phenomenon of dispersion has several important applications:

• Optical Instruments: Dispersion is utilized in devices like spectrometers, which analyze the spectral composition of light.
• Understanding Light Sources: Analyzing the spectrum of light emitted by stars or other celestial bodies helps astronomers understand their composition and properties.
• Creating Spectacles: Prisms can correct vision and enhance clarity for individuals with specific eye conditions.

Natural Occurrences of Dispersion

Dispersion is not limited to artificial setups; it also occurs naturally. One of the most common natural occurrences is the formation of rainbows:

• Rainbows: When sunlight passes through raindrops in the atmosphere, the light is refracted and dispersed, creating a circular arc of colors.

This natural phenomenon exemplifies the principles of dispersion and the beauty of light interacting with different mediums.