Have you ever noticed how a straw in a glass of water seems to be unnaturally bent or out of shape? However, upon removing it, we can clearly see that the straw is, in fact, perfectly fine. This strange phenomenon occurs because of the way light rays behave. Rainbows are another example of an optical illusion that occurs due to the behavior of light rays. In this article, we’ll explore the basic properties of light and see how light acts differently when it passes through certain mediums.
The first thing we need to know is that light is actually made up of many rays that usually travel quite fast in a straight line. Some surfaces, like windows, can easily allow light to pass through. However other surfaces, like mirrors, reflect light. An easy way to think of the concept of reflection is in terms of bouncing. For example, if we throw a tennis ball at the floor, it will bounce up again. In the same way, when light rays hit a surface where it cannot pass through, they are bounced or reflected. In general, light rays reflect back at the exact angle that they strike a surface. If we go back to the example of the mirror, we can now understand why we see our reflections. Light rays strike our faces and then travel toward the mirror. Instantly, they are reflected back at us at the same angle, so that we see our reflections. Scientists refer to this concept as the Law of Reflection. Reflection also depends on the properties of the surface. A mirror reflects a perfectly clean, clear image because it is so smooth. What if we hold a torch in front of a white wall? The wall would also bounce light rays away but they would be diffused. In other words, if we were to stand in front of the white wall with the torch shining directly at it, our own faces and bodies would be lit up softly from the reflected light. Many photographers use this principle to help light up people’s faces when they are shooting a portrait.
Refraction is a word used to describe another way in which light behaves differently. In this case, we are going to look at instances when light passes through a somewhat clear substance. A perfect example is water. Water does allow light to pass through, but not as easily as a piece of clear glass might. Since water has a certain density, it is a little difficult for light rays to pass through it. Instead of passing in a straight line, the light bends a little as it goes though. This is why our straw in a glass of water seems to be bent even though it is actually straight. It is simply a case of light rays playing a trick on our eyes. In much the same way, when it is raining and the sun is out, the sun’s light rays pass through a vast curtain of raindrops. The light rays pass through each raindrop and then go through a process of reflection and refraction as they exit. The entire process causes white light to split into its various different colors, and it appears as a rainbow to us down on Earth.
The world of light and optics is a fascinating subject. By studying these concepts in detail, scientists, researchers, and manufacturers have been able to create many incredible products and technologies to make our lives easier. In other cases, people have even used their knowledge of the properties of light to solve crimes and understand how weather or outer space phenomena work.
The resources below offer plenty of background information and related activities about reflection, refraction, and the properties of light.
More Information on Reflection & Refraction/Light
- A Video Demonstrating Reflection and Refraction
- A Cartoon on Light Absorption in Water
- Isaac Newton and the Glass Prism
- The Law of Reflection of Light
- Light - Reflection and refraction
- The article "Lesson Plan on the Properties of Light" was used
- How Our Eyes Use Reflected Light to See