REFRACTION

REFRACTION OF WAVES

• Refraction:• A change in the direction of waves as they pass from one medium to another,

or of water waves as they encounter a depth change

REFRACTION OF WAVES

• The diagram shows how waves are refracted and how the velocity and wavelength change.

Recall that as waves enter a medium with differing properties, the velocity will change. As water encounters a depth change, the velocity will change.

V2 , λ2

V1 , λ1

REFRACTION OF WAVES

• The change in direction depends on the medium the wave travels out of and the medium the wave travels into

• Keep in mind that when we are talking about refraction, we are talking about a wave crossing a boundary

REFRACTION OF WAVES

• Most of our discussions of refraction will be about light

• ALL WAVES UNDERGO REFRACTION, but we are going to examine refraction of light as it is easier to demonstrate and see

REFRACTIVE INDEX

• Light travels fastest in a vacuum• 3.00*108 m/s• This speed gets the symbol ‘c’ in

physics

• Light is slower in all other mediums

• The ratio of the speed of light in a vacuum to the speed of light in another medium is called the refractive index• The refractive index gets the

symbol n

𝑛=𝑐𝑣

ANGLE OF REFRACTION

• As light enters the new medium, the Normal still exists• Just as in reflection

• The angle of refraction is the angle between the normal and the refracted ray

ANGLE OF REFRACTION

• The angle of refraction depends on the material

• If the wave moves into a material with a higher refractive index:

• n1 < n2

• The velocity slows down• The wave turns toward the normal

• The angle of refraction is smaller than the angle of incidence

ANGLE OF REFRACTION

• If the wave moves into a medium with a lower refractive index

• n1 > n2 • The wave speeds up• The wave turns away from the

normal• The angle of refraction is greater

than the angle of incidence

SNELL’S LAW

• Snell’s law is how we can calculate various parts of a refracted wave

• Keep in mind that n has an equation we can substitute into Snell’s Law