Aim: What happens to Aim: What happens to the speed of light in the speed of light in different mediums?different mediums?

Do Now:

What is the wavelength of yellow light? v = f λ

c = f λ

3 x 108 m/s = (5.20 x 1014 Hz) λ

λ = 5.8 x 10-7 m

Index of Refraction (Index of Refraction (nn)) Equal to ratio of speed of light Equal to ratio of speed of light

(c) in vacuum to speed of light (c) in vacuum to speed of light in materialin material

Indicator of optical densityIndicator of optical density

These are the indices of refraction (n)

A ray of monochromatic light A ray of monochromatic light passes through a flint glass passes through a flint glass

prism. What is the speed of the prism. What is the speed of the light ray in flint glass?light ray in flint glass?

n = c/vn = c/v1.66 = 1.66 = 3.00 x 103.00 x 1088 m/sm/s

vvv = v = 3.00 x 103.00 x 1088 m/sm/s

1.661.66

v = 1.81 x 10v = 1.81 x 1088 m/sm/s

In a certain material, a beam In a certain material, a beam of monochromatic light of monochromatic light

(f=5.09 x 10(f=5.09 x 101414 Hz) has a speed Hz) has a speed of 2.25 x 10of 2.25 x 1088 m/s. What is the m/s. What is the

material?material?n = c/vn = c/vn = n = 3.00 x 103.00 x 1088 m/s m/s 2.25 x 102.25 x 1088 m/s m/s

n = 1.33n = 1.33

WATERWATER

Speed of light is Speed of light is constant…constant…

Large n Large n small v small vSmall n Small n large v large v

Optical DensityOptical Density Velocity of the wave in the Velocity of the wave in the

new medium depends on new medium depends on optical density.optical density.

The more dense, the slower The more dense, the slower the velocitythe velocity

Determines the direction and Determines the direction and degree to which the ray will degree to which the ray will bend upon entering the new bend upon entering the new medium.medium.

A beam of monochromatic A beam of monochromatic light travels through flint light travels through flint glass, crown glass, lucite, glass, crown glass, lucite,

and water. The speed of the and water. The speed of the light is slowest inlight is slowest in

(1)(1)Flint glassFlint glass

(2)(2)Crown glassCrown glass

(3)(3)LuciteLucite

(4)(4)WaterWater

Relationship between n, v, and Relationship between n, v, and λλ

We know:We know:

andand

So we can say: So we can say: