Total Internal Reflection ~ Section 12.5 ~

Total Internal ReflectionWhen light travels from a medium with a high index of refraction to one that is lower (i.e. oil to air) we see refracted ray bend away from the normal.

As the angle of incidence increases so will the angle of refraction in this case.

at one point the angle of Reflection will be at 90o.

Critical Angle: is the angle of incidence that produces a refracted angle of 90o.

Any angle of incidence past the critical angle will produce no refracted ray and only a reflected ray.

Total Internal Reflection: when the angle of incidence is greater than the critical angle.

Neat Examples of Total Internal Reflection

Diamonds sparkle because of their high optical densityand the way they are cut. The sparkle is the result oftotal internal reflection.

Neat Examples of Total Internal Reflection

The coin disappears because the interface between theglass and the water acts like a mirror, reflecting thelight before it hits the coin.

Neat Examples of Total Internal Reflection

Light from a laser can undergo total internal reflectionin a tank of water. The light is “trapped” in the water.

Fibre Optics

Fibre optics are a useful application of total internalreflection. They are used for fast and efficientcommunication (voice, data and video).

Fibre optics are a useful application of total internalreflection. They are used for fast and efficientcommunication (voice, data and video).

1. light is traveling more slowly in the first medium than in the second.

2. the angle of incidence is large enough that no refraction occurs in the second medium. Instead, the ray is reflected back into the first medium.

When does it happen?

Phenomena Related to Refraction

~ Section 12.7 ~

1. Apparent DepthApparent depth: is the depth that an object appears to be due to the refraction of light in a transparent medium.

it will make a object appear closer than it actually is.

Some objects may also appear to “bend”

2. “Flattened” Sun

Light coming from the sun is refracted here to earth i.e. from space (very little air) to earth’s surface (very dense air).

During sunsets the bottom of the sun is refracted more than the top of the sun.

this causes a “flattened” image of the sun rather than round.

3. Water on Pavement ~ The MirageMirage: a virtual image that forms as a result of refraction and total internal reflection in Earth’s atmosphere.

this happens as light travels from cool air into warmer air. where total internal reflection happens at the warm low air.

The sky is being reflected on the road (hot air above road)

When a Moon is out at night above a lake, you can see a shimmering image of the moon on the water’s surface.

at night the air just above the water is warm. Causing total internal reflection inside the warmer air.

4. Shimmering

5. The Rainbowa rainbow is produced by light traveling through rain droplets that act as prisms that separate light.

Each colour will travel through he rain drop at different speeds so different refractions.

Colours hit the back of the raindrop and exits the same side as the sun then go to your eye.