Use Semicircular Blocks to Show Total Internal Reflection Flashcards
What does light going from a material with a higher refractive index to a material with a lower refractive index do?
Speed up and so bends away from the normal e.g when travelling from glass into air
What happens if you increase the angle of incidence?
The angle of refraction gets closer and closer to 90°
What does the angle of incidence eventually reach?
A caricias angle for which r = 90°
What is the light refracted right along?
The boundary
What do you get above this critical angle?
The total internal reflection - no light leaves the medium
What does an experiment to demonstrate this use?
A semicircular block instead of a rectangular one
What is the incident light ray aimed at?
the curved edge of the block so that it always enters at right angles to the edge.
What does this mean?
it doesn’t bend as it enters the block, only when it leaves from the straight edge
How do you investigate the critical angle, C?
Make the positions of the rays and the block on paper and use a protractor to measure I and r for different angles of incidence
Less than the critical angle?
Most of the light passes out but a little bit is internally reflected
Equal to critical angle?
The emerging ray comes out along the surface. There’s a lot of internal reflection
Greater than critical angle?
No light comes out. It’s all internally reflected I.e total internal reflection
Check out diagram page 35
Ok
