Last Updated on May 12 2025
When light passes through a prism, it refracts or bends, turning into a rainbow of colors. It happens because light trels at different speeds through different materials. The amount of refraction depends on the difference in speed and the angle of incidence at which light hits the material.
When light passes through a prism, you鈥檒l see a rainbow of colors on the other side. Since violet light has the highest frequency, it has the higher refraction.
Meanwhile, red light refracts the least due to its low frequency. So, let鈥檚 learn more about the passage of light through a prism.

Refraction is the change in the direction of a we due to a change in speed. It is commonly observable when wes move from one medium to another.
For example, when light wes move from air to water, they are refracted. The amount of refraction depends on the indices of refraction of the two materials. It also depends on the angle at which the wes move.
The refraction index measures how much a we is bent when it moves from one medium to another. The higher the index of refraction, the more the we is bent.
Refraction is responsible for many optical effects, such as the bending of light at a glass surface and the formation of images in lenses and mirrors.
Why Does a Rainbow Form When White Light Passes Through a Prism?
Image By: BlenderTimer, Pixabay
When shining a beam of white light through a glass prism, you will see a rainbow of colors. Each color represents a welength of light. For example, violet light has the shortest welength, and red light has the longest welength.
It鈥檚 the same phenomenon that forms the rainbow after the rain. When light hits a raindrop, it bends (refracts) and then splits up into different colors. In this case, the raindrops act as tiny prisms.
The visible spectrum of light forms the colors of a rainbow: red, orange, yellow, green, blue, and violet.
Isotropic materials are commonly used to make prisms. An isotropic material has the same physical properties in all directions. It means that an isotropic material will refract light equally in all directions. That鈥檚 why a prism does such a splendid job of splitting light into different colors.
Which Colors Do You See When Light Passes Through a Prism?You see a spectrum of colors when white light passes through a prism because the different welengths of light bend in different amounts as they pass through the prism. The human eye can only distinguish primary colors: red, blue, and green.
All other colors of the rainbow you see are formed by mixing these three colors in different proportions because different colors correspond to different welengths of light. These are called secondary colors.

Image Credit: ArcturianKimona, Pixabay
All types of prisms he different properties. Plus, they alter light in different ways.
Dispersive PrismsA dispersive prism disperses or separates light into its different colors. In other words, it takes white light and breaks it up into all of its colors. That鈥檚 why a dispersive prism is also called a rainbow maker.
The most common type of dispersive prism is the triangular prism. Some others include: Amici Prism: It’s a compound prism present in spectrometers. Granite Prism: It has a long cross-section and is used for large-scale projects. Abbe Prism: The Abbe prism is used in periscopes and has two 90-degree angles. Reflective PrismsSome prisms reflect light rather than refract it. These prisms are common in single-lens reflex cameras and binoculars.
Without these reflective prisms, you鈥檒l see things upside down through your binoculars or camera. An example of these prisms is the Abbe-Koeing prism. It has four internal reflections.
Other examples include the Dove prism, Corner-cube retroreflector, roof pentaprism, and Perger-Porro prism.
Polarizing PrismsPolarizing prisms work on the principle of birefringence. They can split a beam of light into two beams with different polarization.
Polarizing prisms are used in many optical instruments, such as polarimeters. They can also be used to make polarized sunglasses.
Some examples of these prisms are: Glan鈥揊oucault prism Glan鈥揟aylor prism Nicol prism Glan鈥揟hompson prism Rochon prism S茅narmont prism How Does Refraction Play a Role in Dispersion?
Image Credit: Mauro_B, Pixabay
The degree to which light is bent depends on the index of refraction. The index of refraction refers to how much a material slows down the speed of light as it passes through that material.
Air鈥檚 refractive index is 1.0003, meaning that light trels slightly slower in the air than in a vacuum. Meanwhile, water has a refraction index of 1.33. So, again, it means the light will trel slowly through the water.
How Can You Observe the Refraction of Light?Refraction is an important property of light that allows us to see the world around us. Light wes change direction as they trel from one medium to another.
You can notice refraction easily if you he a glass of water and a pencil. Here's what to do: Fill a glass with water. Place a pencil in the water so that it is pointing straight up. Look at the pencil inside the glass. The pencil will appear to be bent.The pencil appears bent because the light wes are refracting, or changing direction, as they trel from the water to the air.
Since water has a higher refractive index than air, the light wes slow down as they enter the water. As a result, it causes the wes to bend.
You can also see refraction when you look at an object in the water. For example, when you are swimming and see the bottom of the pool, it appears closer than it actually is because the light wes are bent as they trel from the water to your eyes.

When passing through a prism, light splits into all the rainbow colors. Each color is a different welength of light. As a result, the different colors will bend or refract at different angles.
The angle of refraction depends on the welength of the light. Shorter welengths bend more than longer welengths. For example, because red light has a longer welength than violet light, red light bends less than violet light.
We see different colors because our eyes perceive different welengths of light in different ways.
Sources https://flexbooks.ck12.org/cbook/cbse-physics-class-10/section/2.3/primary/lesson/refraction-of-light-through-prism/ https://www.physicsclassroom.com/class/refrn/Lesson-4/Dispersion-of-Light-by-Prisms https://micro.magnet.fsu.edu/optics/activities/teachers/prisms.html https://sciencing.com/happens-light-passes-through-prism-8557530.html https://byjus.com/physics/refractive-index/#how-does-the-refractive-index-vary-with-welength https://en.wikipedia.org/wiki/Prism 聽Featured Image Credit: Dobromir Hristov, Pexels
Table of Contents
What Is Refraction?Why Does a Rainbow Form When White Light Passes Through a Prism?Which Colors Do You See When Light Passes Through a Prism?What Are the Types of Prisms?Dispersive PrismsReflective PrismsPolarizing PrismsHow Does Refraction Play a Role in Dispersion?How Can You Observe the Refraction of Light?Final Thoughts