REFRACTIONREFRACTION

What is Refraction?What is Refraction? RefractionRefraction is the bending of light is the bending of light

rays as they travel from one medium rays as they travel from one medium to another.to another.

MediumMedium – a material that is part of a – a material that is part of a process.process.

The cause of refraction is the The cause of refraction is the changing in the speed of light as it changing in the speed of light as it travels through the various media. For travels through the various media. For example, the speed of light slows example, the speed of light slows down as you go from air to water.down as you go from air to water.

RefractionRefraction

The light from the The light from the spoon is bent at the spoon is bent at the surface of the water. surface of the water. This makes the spoon This makes the spoon appear broken.appear broken.

The Speed of LightThe Speed of Light Light can travel at a speed of Light can travel at a speed of 300,000 300,000

km/skm/s in a vacuum – a space with little in a vacuum – a space with little or no particles in it.or no particles in it.

This means that light travels This means that light travels 300million metres every second! 300million metres every second! ((300,000,000 m/s300,000,000 m/s))

As more particles get in the way, it As more particles get in the way, it gets harder for light to get from one gets harder for light to get from one place to another. The particles slow place to another. The particles slow down the passage of the waves that down the passage of the waves that make up the light.make up the light.

The Index of RefractionThe Index of Refraction The The index of refractionindex of refraction is a list that gives you an is a list that gives you an

idea of how easily light waves can travel through a idea of how easily light waves can travel through a medium. The higher the number, the harder it is medium. The higher the number, the harder it is for light to travel through the medium.for light to travel through the medium.

A vacuum is 1.0 – the easiest for light to travel A vacuum is 1.0 – the easiest for light to travel through.through.

Air is 1.003 and water is 1.33.Air is 1.003 and water is 1.33.

To calculate the index of refraction for a material:To calculate the index of refraction for a material:

Index of refraction = Index of refraction = speed of light in vacuumspeed of light in vacuum speed of light in mediumspeed of light in medium

n = n = cc vv

How Light RefractsHow Light Refracts A light beam contains several rays – A light beam contains several rays –

all traveling parallel at the same all traveling parallel at the same speed.speed.

It strikes the surface of the new It strikes the surface of the new medium and “bends” because the medium and “bends” because the particles of the new medium particles of the new medium interfere with its movement.interfere with its movement.

The light rays then travel parallel at The light rays then travel parallel at the same speed, but, in the new the same speed, but, in the new direction in which they were bent.direction in which they were bent.

How Light RefractsHow Light Refracts

Drawing Refraction DiagramsDrawing Refraction Diagrams Draw a line the that is at 90° to the surface where the two Draw a line the that is at 90° to the surface where the two

media meet – this is the media meet – this is the normalnormal. The normal is drawn . The normal is drawn where the incident beam strikes the second medium.where the incident beam strikes the second medium.

Drawing Refraction DiagramsDrawing Refraction Diagrams Now you have to consider the two materials…Now you have to consider the two materials…

• If you are going from If you are going from low refractive index to a higher onelow refractive index to a higher one – – the light bends toward the normal. the light bends toward the normal. (Air 1.003 (Air 1.003 water 1.33) water 1.33)

Drawing Refraction DiagramsDrawing Refraction Diagrams Again, consider the two materials…Again, consider the two materials…

• If you are going If you are going higher to lowerhigher to lower – the light will bend away – the light will bend away from the normal. from the normal. (Water 1.33 (Water 1.33 Air 1.0003) Air 1.0003)

Refraction Video – Bill Nye!!!Refraction Video – Bill Nye!!!

THE ENDTHE END