Reflection is the change in direction of a light wave. The light bounces off a surface and then heads back. We see because we see light. We see a reflection because the light is coming back to us. We see our reflection in a mirror. The light bounces off of us, bounces off the mirror, and comes back to our eyes, and we see ourselves.

Walking reflection This picture shows a reflection on sand and water.

   Reflection angles

This diagram shows light coming from P, bouncing off a mirror, and heading in the direction of Q.

Refraction is the change in direction of a wave, caused by the change in the wave’s speed. Examples of waves include sound waves and light waves. Refraction is seen most often when a wave passes from one medium to a different medium. Different types of medium include air and water.

When a wave passes from one medium to another medium, the wave will change its speed and its direction. For example, when a light wave travels through air and then passes through water, the wave will slow and change direction.

As light travels through the refractive device, it will ‘bend’ toward the normal. When it leaves the refractive device to air (with a lower refractive index) it will return along the same angle as when it entered the device.

An example of how refraction works is placing a straw in a cup of water, with part of the straw in the water. When looking at a certain angle, the straw appears to bend at the water’s surface. This is because of the bending of light rays as they move between the air and the water.

When viewing at a certain angle, the straw appears to bend, due to refraction of light as it moves into the air. See the picture below.

Refraction In A Glass Of Water Photograph by Science Photo Library

Below, the picture shows light on air–plexi surface. It shoes refraction and reflection.
ProFizika Fénytörés III Optikai lencsék - YouTube


(edited from sources onetwo)

CC BY-SA 3.0