Aim: How can we explain Snell’s Law?

Do Now:

What is the speed of light in zircon?

Refraction• Waves that are transmitted through

a boundary often change direction when entering the new medium. This bending of the path of waves is called REFRACTION.

Air

Transmitted Ray is Refracted

Light Wave

Water

Optics Demo

Effects of Refraction

Snell’s Law

2211 sinsin nn

A beam of light strikes a crown glass block at an angle of 60o.

What is the angle of refraction?

n1sinθ1 = n2sinθ2

(1.00) sin (60o) = (1.52) sin θ2

sin θ2 = (1.00) sin (60o)

(1.52)

θ2 = 35o

An incident ray in lucite is refracted through water. If the

incident ray is at an angle of 50o, what is the angle of refraction?

n1sinθ1 = n2sinθ2

(1.50) sin (50o) = (1.33) sin θ2

sin θ2 = (1.50) sin (50o)

(1.33)

θ2 = 60o

Less Dense to More Dense

• Light is traveling from a FASTER to a SLOWER medium

• The light will bend towards the normal.

• Ex: Air to water

More Dense to Less Dense

• Light is traveling from a SLOWER to a FASTER medium

• The light will bend away from the normal line.

• Ex: Water to Air

But what if the light is not entering the new medium at an angle?

THE LIGHT WILL NOT BEND!!

No Refraction

Air

Water

Relationship between v and λ

• FREQUENCY IS CONSTANT

v = fλ• v increases λ increases

• v decreases λ decreases

As a monochromatic beam of light passes obliquely from flint

glass into water, how do the characteristics of the beam of

light change?(1) Its wavelength decreases and its frequency

decreases.(2) Its wavelength decreases and its frequency increases.(3) Its wavelength increases and it bends toward the

normal.(4) Its wavelength increases and it bends away from the

normal.

Trace the path of the ray

Flint glass

Lucite

Diamond

If a ray exits to the same material it started in, the incident angle is equal to the final refracted angle!

θ

θ