Water Refraction Experiment (Video)

Have you ever noticed that things look strange when you view them through a glass of water?

It’s not just because of imperfections in the glass; there’s a fascinating scientific phenomenon at work.

When light waves pass from one transparent substance to another, such as from air to water or air to glass.

The speed of light changes as it enters a different medium. When light travels through denser materials like water or glass, it slows down.

This change in speed affects the direction of the light, causing it to bend. This bending of light is what we call refraction.

Refraction is the bending of light as it passes from one transparent medium into another​1​

Let’s explore a simple water refraction experiment using everyday materials like a glass of water placed in front of a sheet of paper.

In this experiment, we observe the phenomenon of refraction in action.

This fun and educational activity will help kids and adults understand how light bends through different mediums, such as air, water, and glass.

With just a glass of water, a few graphics, and some creativity, you can observe the bending of light and explore the scientific principles behind this phenomenon.

Here are two simple and fun water refraction experiments.

Water Refraction - Light Science Experiment

Refraction of Light in Water

Prep Time: 30 minutes
Active Time: 10 minutes
Total Time: 40 minutes

Here is an easy science experiment you can do to "wow" your kids or friends. It's super simple and you can set it up within minutes.


  • water
  • graphics you want to see the changes


  • a clear glass or jar
  • adult supervision


  1. Place the glass in front of the graphics.
  2. Adjust the distance between the glass and the graphics until the image can be seen clearly through the empty glass.
  3. Slowly pour the water in and see what happens.
    smiling face behind glass, water poured into the glass, reversed smiling face behind glass full of water
    arrow points right behind glass, arrow points left when the glass is full of water

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  • Do the experiment again using different distances between the glass and the graphics
  • Try glasses and jars of different shapes.
  • Try using different liquids such as oil, juice, etc.

The Science of Light Refraction

Light refraction is a science key concept wherein light changes direction as it moves from one substance to another due to a difference in densities.

For instance, when light travels from air to water or glass, it slows down and bends. This bending of light causes objects viewed through these substances to appear distorted or displaced.

The angles at which the light enters and exits the substance play an important role in determining the level of distortion.

Transparent materials like lenses and prisms can also influence light refraction, and a simple glass of water can be a great example to explore these principles.

Our eyes and corrective lenses utilize the same refraction principles to help us focus and perceive the world more clearly.

Exploring Refraction and the Bending of Light with Water and Glass

Refraction Experiment - bending of light from air to water

The Water Refraction Experiment used a clear glass or jar filled with water and placed in front of the graphics you want to see the changes.

Adjusting the distance between the glass and the graphics allows us to observe how the image changes as the light passes through the water and the glass.

Trying glasses and jars of different shapes or using various liquids, such as oil or juice, can further enhance this exploration of light refraction.

When we look at objects through a glass cup of water, the light coming from those objects goes through multiple refractions.

As the light enters the cylindrical glass from the surrounding air, it bends or refracts due to the change in density between the air and the glass.

This bending of light continues as it passes from the glass into the water, encountering another change in density.

When the light exits the water and enters the air or a shallower layer and then again passes from the glass with water to the air, it undergoes additional refractions.

These repeated light refractions create interesting effects we can observe during the experiment.

Illustration of refraction of light after passing through a glass of water

The Role of Density and Temperature

The density and temperature of the medium through which light travels impact how light bends or refracts.

When light passes through a denser material, such as water, it slows down and changes direction more significantly.

This phenomenon is influenced by the density of the water and the transition from air into water.

Likewise, changes in air temperature or the temperature of liquids can affect the refraction angle. As temperature alters the density of the medium, it can lead to different degrees of light bending.

Exploring the Water Refraction Experiment with cold water or liquids at different temperatures can provide fascinating insights into how temperature, density, and light refraction are interconnected.

Additional Observations and Experiments

The Magical Water Experiment presents exciting opportunities for further investigation.

By adjusting the angle at which light enters the glass or jar, we can observe different refraction angles and more pronounced changes in the images.

Exploring transparent mediums, such as prisms or substances with different densities, allows us to understand how light bends and how density influences refraction.

The fun water refraction experiments provide valuable hands-on learning experiences that allow us to explore the intricate relationship between light and matter.

The best part is that these experiments can be conducted using simple, affordable, and easily accessible materials.

The experiment offers a fantastic way to delve into the captivating world of light refraction.

A fun, educational, and engaging activity, the Water Refraction Experiment brings the magic of science to life for kids and adults alike.

Science Kits And Books On Light


  1. 1.
    Jiang W, Chen RT, Lu X. Theory of light refraction at the surface of a photonic crystal. Phys Rev B. June 2005. doi:10.1103/physrevb.71.245115

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