Refraction (T3) Flashcards
Describe refraction..
Sound and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction and this effect is known as refraction.
In what scenario would refraction NOT take place?
If the waves cross the boundary of two substances at 90 degrees. In this case the waves would carry straight on.
What physical occurrence can the behaviour of sound and light be likened to?
Like the water waves in a ripple tank.
What happens to light during refraction? Give an example..
It slows down when entering a denser material than air.
For example, if you look down into a swimming pool, the swimmers will actually appear less deep than they are, because the light is slower in water and will seem to bend when it speeds back up in the air.
Describe the relationship between a light ray entering a flat sheet of glass and the normal…
As a light wave enters the sheet of glass it slows down and bends towards the normal.
Glass is denser than air, so a slower material to travel through.
When the light leaves the glass and re-enters the air, it again bends away from the normal and at the same angle as it was upon entering.
Light entering a denser material will…
Bend towards the normal.
Light entering a less dense material will…
Bend away from the normal.
What is the refractive index of a material?
The refractive index of a material is a measure of how much it slows light down.
What is Snell’s Law and what does it state?
Snell’s law is the law of refraction.
It states:
n = sin i / sin r
Where…
n = refractive index of the material i = angle of incidence in degrees r = angle of refraction in degrees
What can be reflected an refracted?
Light
When light passes from a medium such as glass into air, the angle of refraction is always larger than the angle of incidence.
What is the maximum angle of refraction possible, what is this known as, and why?
- the maximum angle of refraction possible is 90 degrees
- this is known as the ‘critical condition’ as it marks a change in the behaviour of the light
- if it goes any further, the light will be reflected back into the glass