Prepare to Learn Explain the Physics of the picture you printed for homework to the person next to you. Be prepared to feedback to the whole class

Refraction

Objectives To understand what causes a wave to Refract (knowledge) To apply your understanding of refraction to be able to draw wave front diagrams (application) To appreciate the conditions required for refraction (Knowledge) To create your own analogy for refraction (synthesis)

This causes the light to bend or refract. Why is light refracted? The speed of light depends on the material through which the light is travelling. When light enters a different material (e.g. from air into glass), the speed of light changes. This causes the light to bend or refract. glass air The speed of light is affected by the density of the material through which it is travelling. When light enters a more dense medium (from air into glass), its speed decreases and this is why refraction occurs.

Construct – collecting data Copy the table into your book Bring your book and a pen around the whiteboard You are going to complete the table Angle of Incidence (i) Angle of refraction (r)

Refraction at the air-glass boundary

Looking for Patterns What do the results show? Are there any patterns? What is the relationship between I and r?

Refraction in a glass block What do you notice about the angle the light leaves the block at?

Mini-Review - Refraction ray diagram

Apply to Demonstrate

Imagine a car driving over smooth cement towards thick, sticky mud When light enters a more dense medium (from air into glass), its speed decreases and this is why refraction occurs. Imagine a car driving over smooth cement towards thick, sticky mud Thick mud Smooth cement

When light enters a more dense medium (from air into glass), its speed decreases and this is why refraction occurs. When the car meets the mud, the wheel that hits it first will slow down Thick mud Smooth cement

The other front wheel goes at the same speed When light enters a more dense medium (from air into glass), its speed decreases and this is why refraction occurs. The other front wheel goes at the same speed Thick mud Smooth cement

When light enters a more dense medium (from air into glass), its speed decreases and this is why refraction occurs. This turns the car as it heads across the mud. This is what happens to the wavefronts of light Wavefronts Thick mud Smooth cement

This ‘design/create’ skill should challenge you! Your task You are going to come up with your own analogy for refraction. You will draw it in stages, like the one you’ve just seen, with clear explanations along the way  To access grades B-A* your annotations will need to be clear, and explain your analogy clearly. This ‘design/create’ skill should challenge you! Did you know inventing stuff is one of the highest order thinking skills?

Mini-Review - What happens during refraction?

HSW - Effects of refraction Refraction causes visual effects such as this ruler appearing to be bent. This happens because light from the part of the ruler in the water is refracted as it travels from the water into the air. How does refraction make this stone look closer to the surface of the water than it really is? Light rays from the stone are refracted as they leave the water. The brain assumes that these rays have travelled in straight lines and is fooled into forming an image where it thinks the image actual location light rays came from.

Effects of refraction – the Archer fish The Archer fish is a predator that shoots jets of water at insects near the surface of the water, e.g. on a leaf. The Archer fish allows for the refraction of light at the surface of the water when aiming at its prey. image of prey prey location The fish does not aim at the refracted image it sees but at a location where it knows the prey to be.

Refraction summary

Refraction – true or false?

Objectives review To understand what causes a wave to Refract (knowledge) To apply your understanding of refraction to be able to draw wave front diagrams (application) To appreciate the conditions required for refraction (Knowledge) To create your own analogy for refraction (synthesis) Have you met them all? How? Tell the person next to you how well you have done this lesson, and whether you’ve met the objectives or not!