Refraction

What is Refraction? The bending of light as it travels from one medium to another.

Examples of Refraction A spoon appears bent as it enters water. Attempting to touch an object under water and missing it.

Examples of Refraction Seeing an object just under the surface of water in a dish, when you could not see it without the water (Bill Nye!)

What Causes Refraction? The speed of light is different in different mediums. You see things because of the light rays reflecting from them As rays pass through a boundary, the light rays speed up or slow down causing them to bend

Analogy….. Wagons travelling from a paved road to sand.

Explanation….. As the right front wheel hits the sand, the wagon changes direction because the wheel in the sand turns slower.

Refraction Fast Medium Slow Medium

Relative Speeds of Light Faster Slower Vacuum Air Water Acrylic (clear plastic)

The thicker the medium, the slower the light goes Thickness is known as optical density (reflected in the index of refraction value)

Refraction Light Rays incident ray refracted ray angle of refraction angle of incidence angle of refraction

Rules for Refraction The incident ray and the refracted ray are on opposite sides of the line that separates the two media.

Rules for Refraction Light bends towards or away from the normal depending on the speed of light in the second medium.

Rules for Refraction Light bends toward the normal if it travels more slowly in the second medium than in the first.

Faster to slower medium Slower to faster medium Bends towards the normal Slower to faster medium Bends away from the normal

Rules for Refraction Light bends away from the normal if it travels faster in the second medium than in the first.

Partial Reflection Reflection and refraction often happen together. Light hitting the water reflects off the water, but also refracts as it enters the water illuminating objects below the water.

Reflection AND Refraction

Examples of Partial Reflection Glass may have special film to allow light in, but reflect incident light as well.(mirrored buildings) Mirrored surfaces you can see through, but others cannot! (sunglasses)

Refraction Angle of Refraction Vocabulary! Refraction Angle of Refraction

Homework! Pg. 519 #2 – 5