Refraction of LightRefraction of Light

RefractionRefraction

The bending of light as it travels, at an angle, from a material with one refractive index to a material with a different refractive index.

Light travels at a constant speed and a straight line as long as it is in the same medium

The bending of light as it travels, at an angle, from a material with one refractive index to a material with a different refractive index.

Light travels at a constant speed and a straight line as long as it is in the same medium

Fermat’s PrincipleFermat’s Principle

Light will choose the path that takes less time to travel through

Light will choose the path that takes less time to travel through

Using Rays to Describe Refraction

Using Rays to Describe Refraction

Reflected ray and incident ray are the same.

Refracted ray: the ray that is bent upon entering a second medium.

Angle of refraction: the angle between the normal and a refracted ray (represented by upper-case R)

Reflected ray and incident ray are the same.

Refracted ray: the ray that is bent upon entering a second medium.

Angle of refraction: the angle between the normal and a refracted ray (represented by upper-case R)

Direction of Refracted RayDirection of Refracted Ray

When a light ray travels from a medium where the speed is faster (air) to a medium where it’s slower (water), the refracted ray bends toward the normal.

When a light ray travels from a slow medium to a fast medium, the refracted ray bends away from the normal.

When a light ray travels from a medium where the speed is faster (air) to a medium where it’s slower (water), the refracted ray bends toward the normal.

When a light ray travels from a slow medium to a fast medium, the refracted ray bends away from the normal.

Index of RefractionIndex of Refraction

Is the ratio of the speed of light in a vacuum to the speed of light in a given medium.

n = c v

n is the index of refraction c is the speed of light in a vacuum v is the speed of light in a medium

Is the ratio of the speed of light in a vacuum to the speed of light in a given medium.

n = c v

n is the index of refraction c is the speed of light in a vacuum v is the speed of light in a medium

DispersionDispersion The process of separating colours by refraction. White light includes all the wavelengths of

visible light. When you shine white light through a prism,

the light is separated due to each colour having a different wavelength and therefore move at different speeds.

The process of separating colours by refraction. White light includes all the wavelengths of

visible light. When you shine white light through a prism,

the light is separated due to each colour having a different wavelength and therefore move at different speeds.

Problems…Problems… Calculate the speed of light in fused

quartz. Step 1: look up the index of refraction for

fused quartz in Table 11.1 on page 454. (standardized values)

Step 2: write the equation n= c/v Step 3: substitute and solve

1.46 = 3.00 x 108 m/sv

1.46v = 3.00 x 108 m/s v = 2.05 x 108 m/s

Calculate the speed of light in fused quartz.

Step 1: look up the index of refraction for fused quartz in Table 11.1 on page 454. (standardized values)

Step 2: write the equation n= c/v Step 3: substitute and solve

1.46 = 3.00 x 108 m/sv

1.46v = 3.00 x 108 m/s v = 2.05 x 108 m/s

You Try It!You Try It!

P. 455 # 1-4 P. 456 # 1-3, 5, 8.

P. 455 # 1-4 P. 456 # 1-3, 5, 8.