Introduction

Light behaves as a wave, which means it can exhibit several wave phenomena when it interacts with materials, particles, or openings. These behaviors help explain many natural events such as rainbows, blue skies, colorful soap bubbles, and patterns produced by light passing through narrow slits.

Understanding these wave behaviors allows scientists to develop technologies such as spectroscopy, optical instruments, communication systems, and imaging devices.

The major wave behaviors of light include:

• Dispersion
  
  

• Scattering
  
  

• Interference
  
  

• Diffraction
  
  

Each phenomenon occurs because light waves interact with matter or with other waves.

Dispersion

What is Dispersion?

Dispersion is the separation of white light into its different colors because different wavelengths of light bend by different amounts when passing through a material.

White light is composed of many colors in the visible spectrum, including:

• Red
  
  

• Orange
  
  

• Yellow
  
  

• Green
  
  

• Blue
  
  

• Indigo
  
  

• Violet
  
  

When white light passes through a prism, each color refracts at a slightly different angle. This causes the light to spread out into a rainbow-like pattern.

Examples of Dispersion

• Light passing through a glass prism
  
  

• Formation of a rainbow in the sky
  
  

• Color separation in spectroscopy
  
  

Why Dispersion Happens

Different colors of light have different wavelengths, and each wavelength travels at a slightly different speed in a material. Because of this difference in speed, the colors bend at different angles.

Scattering

What is Scattering?

Scattering occurs when light is redirected in many directions after interacting with particles or molecules in a medium.

The amount of scattering depends on the wavelength of the light and the size of the particles.

Examples of Scattering

Blue Sky

The sky appears blue because shorter wavelengths (blue light) scatter more easily in Earth's atmosphere than longer wavelengths.

Red Sunset

During sunrise or sunset, sunlight travels through a longer path in the atmosphere. Most of the blue light is scattered away, leaving mainly red and orange wavelengths visible.

Fog and Clouds

Water droplets scatter light in many directions, which is why clouds appear white or gray.

Interference

What is Interference?

Interference occurs when two or more waves overlap and combine. The result can be either:

• Constructive interference – waves combine to produce a stronger wave
  
  

• Destructive interference – waves cancel each other out
  
  

Examples of Interference

Soap Bubbles

Thin films of soap create colorful patterns because different wavelengths interfere with one another after reflecting from the film.

Oil on Water

The rainbow-like colors seen in oil spills are caused by thin-film interference.

Optical Coatings

Many lenses and glasses use coatings that rely on interference to reduce reflections.

Diffraction

What is Diffraction?

Diffraction is the bending of waves around obstacles or through narrow openings.

Although diffraction occurs with all types of waves, it becomes most noticeable when the opening or obstacle is similar in size to the wavelength.

Examples of Diffraction

Light Through a Narrow Slit

When light passes through a small slit, it spreads out and produces patterns of bright and dark fringes.

Sound Around Corners

Sound waves can bend around obstacles, which is why you can hear someone speaking even if they are around a corner.

Diffraction Gratings

Scientists use diffraction gratings to analyze light spectra and determine the composition of stars and materials.