Refraction What is Refraction The bending of light

$Refraction$

Refraction

$What is Refraction? • The bending of light as it travels from one medium$

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

$Examples of Refraction • A spoon appears bent as it enters water. • Attempting$

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

$Examples of Refraction • Seeing an object just under the surface of water in$

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!)

$What Causes Refraction? • The speed of light is different in different mediums. •$

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

$Refraction Fast Medium Slow Medium$

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)

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

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

$Rules for Refraction 1. The incident ray and the refracted ray are on opposite$

Rules for Refraction 1. The incident ray and the refracted ray are on opposite sides of the line that separates the two media.

$Rules for Refraction 2. Light bends towards or away from the normal depending on$

Rules for Refraction 2. Light bends towards or away from the normal depending on the speed of light in the second medium.

$Rules for Refraction Light bends toward the normal if it travels more slowly in$

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 ▫ Bends towards the normal • Slower to faster medium ▫ Bends away from the normal

$Rules for Refraction Light bends away from the normal if it travels faster in$

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

$Partial Reflection • Reflection and refraction often happen together. ØLight hitting the water reflects$

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

$Reflection AND Refraction$

Reflection AND Refraction

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

$Vocabulary! Refraction Angle of Refraction$

Vocabulary! Refraction Angle of Refraction

Homework! Pg. 519 #2 – 5