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.
|