Understanding Light: Reflection, Refraction, and More
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Understanding Light
What is Light?
Light is a form of electromagnetic energy. Very small particles called photons move in a wave pattern.
Visible light is the light which allows you to see the colours and shapes of objects. Light can come from a natural source or an artificial source.
Some objects only emit light which they receive from other light sources. In this case, they absorb some of the light, and reflect the rest in all directions.
Objects can be transparent, translucent, or opaque. This depends on how light travels through them.
How Does Light Travel?
Light travels in a straight line. It travels in waves and does not require a medium. The speed of light, however, does depend on the medium. The speed of light in a vacuum and in the air is similar: about 300,000 km/sec.
How is Light Reflected?
When a ray of light hits a surface, it bounces off and begins to travel in a different direction. The incident ray hits the surface. The reflected ray bounces off the surface. All matter reflects a certain amount of light. When a surface is shiny and smooth, the reflection is more noticeable, for example, a mirror or a still body of water.
How is Light Refracted?
Light is refracted when it passes from one medium to another medium which has a different density. In this situation, instead of bouncing back, light bends at the boundary between the two media.
Water is denser than air, so light is refracted when it travels through the surface of the water. The flower stem in the photo is partly under water, so it appears to be bent.
Lenses and Refraction
Lenses are discs made of glass or plastic with one or two curved faces. They refract light. There are two types:
Converging Lenses
They are thicker at the centre than at the edges. They concentrate the rays of light. A magnifying glass is an example of a converging lens.
Diverging Lenses
They are thicker at the edges than at the centre. They disperse the rays of light. People who are short-sighted have these kinds of lenses in their glasses.
How Eyes See Colors
Visible light waves are the only electromagnetic waves visible to the human eye. Eyes can see these waves as the colours of the rainbow. Each colour has a different wavelength. Red has the longest wavelength and violet has the shortest. All the waves together form white light, including infrared and ultraviolet light.