The Refraction of Light

Right now… Open up your the Science Focus 8 Textbooks to page 200 and of the Science in Action handouts. Big Idea: Know what refraction is, when it occurs, and how it is different from reflection.

Refraction of Light What Does the “Refraction” of light mean? What causes light to refract? Who can explain why light refracts?

What is Refraction Refraction is the bending of light as it changes speeds when it moves from one medium to another The speed of light changes due to the density of the medium which causes the light to bend or refract

Refraction Analogy Imagine winter driving conditions when the road is plowed but the shoulder is covered in deep snow! If one set of tires on one side of your car hit that snowy shoulder, that side of the car slows down and the whole car is sucked (bent) toward the ditch… the same thing happens with light. Also, if the snow in the shoulder is light and dry and only 2 inches deep, will it pull the vehicle off the road as fast if the snow is 12 inches deep and wet & slushy?

What is Refraction? Refraction occurs when light is slowed down by a denser material When one “corner” of a beam of light strikes the denser material 1 st, it is slowed down bending the beam of light toward that corner Normal line

What is Refraction? Please copy down this diagram making note of the normal line, ray of incidence, ray of refraction, angle of incidence, and angle of refraction. Normal line

Density is Key The key to bending light is to change the… DENSITY The more dense the material, the more it will bend the light

Angles of Refraction Normal Line A question like this could be worth 8 marks What if I switched the more dense and less dens materials… what would the diagram look like then Less dense More dense

If Density Changes? Water = Least Dense Normal Line Oil = More Dense Molasses = Most Dense Normal Line Ray of Incidence

If Density Changes? Water = Least Dense Normal Line Oil = More Dense Molasses = Most Dense Normal Line Ray of Incidence Lowest density = Least Refraction Most density = Most Refraction More density = More Refraction

How does this affect you? When you look at something in the water… are you looking straight at it?

Refraction & Sight If you are trying to grab something in the water, you will need to make an adjustment because of refraction You should be able to diagram where an image of an object appears to be when looking at it from above, and where the object actually is… as well as the angles of reflection and refraction

Straight on view How is this fish automatically compensating for refraction?

The other way around By positioning itself straight under the target, there is no “angle” of refraction so the light is not bent and light passes straight through putting the object and the image in the same spot.

Increasing the Angle The greater the angle of incidence, the greater the angle of refraction!

Demo Time Watch what happens as we change the angle we shine it into the tank of water!

What is a Mirage? What is a Mirage and what creates them?

What is a Mirage? A mirage is formed when air near the ground warms… warm air is less dense than cold air… so light is bent As a result, light from the sky directed at the ground is bent upward as it enters the less dense air. The “pools of water” are actually images of the sky refracted by warm air

How does this affect you? When you look at something in the water… are you looking straight at it?

Refraction & Sight If you are trying to grab something in the water, you will need to make an adjustment because of refraction You should be able to diagram where an image of an object appears to be when looking at it from above, and where the object actually is… as well as the angles of reflection and refraction

The Big Idea!!! Refraction of light depends on two things: The DENSITY of the medium The ANGLE the light strikes the medium If you decrease the density… you will decrease how much the light is bent If you decrease the angle of incidence… you will decrease how much the light is bent.