Light travels in transverse waves. This means that the deflection of the wave runs across the direction of travel of the wave.

This is similar to water waves.  in the video the waves move out from the larger boat but the fishing boat only moves up and down.

Reflection

Reflection is how light bounces off an object. the smoother the surface, the more regular the reflection. an example of this is polishing a pair of shoes. it starts off rough so looks dull. as you polish the shoes the surface gets smoother and smoother making the reflection more regular.  It is possible to polish them so that you can see your face in them.  The mirror takes this to its logical conclusion.

The law of reflection

The law of reflection states that

 the angle of incidence = the angle of reflection

This applies to both smooth and rough surfaces.  Remember to draw a “normal” (imaginary line at right angles to the surface WHERE THE INCIDENT RAY STRIKES)

Refraction.

When light goes from one substance to another it either slows down or speeds up depending on the relative densities of the materials. the denser the material the slower the light travels.  If the light strikes the surface between the materials at any other angle than a right angle the light will bend.

This can be seen in every day experiences such as a pencil “bending” in water or strange effects in a swimming pool.

This interactive refraction simulator applet might also help

Total internal reflection

As mentioned above when light goes from one medium to another it bends if the angle of entry is not a right angle. As the angle of incidence increases the refracted ray gets closer and closer to the critical angle where the light ray lines up with the interface.  at any angle greater than the critical angle the light will be reflected back into the medium to cause total internal reflection. this can be used in every day life in periscopes, cat eyes in the road and other uses.

Colour

As Sir Isaac Newton proved with his “Crucial Experiment”, white light is a mixture of colours. These can be separated using a prism. We se a red object as red because it absorbs all colours of light except red which it reflects.  Blue objects reflect blue light but absorb all other colours.

If you put a blue object under red light it will appear black as blue objects only reflect blue light. as there is no blue light in red light, no light is reflected so it appears black.

Check out these flash animations to see what I mean. (Pun intended)

Image under a red filter

Image under a green filter

Image under a blue filter

A fruit bowl (You can change the colour of light on this one.)

For a more detailed look at light check out the page on my theatre web site. this is not part of CE but for interest only.