Refraction D. Crowley, 2008

Refraction To be able to apply your knowledge of refraction to explain new situations

Refraction Light travels in straight lines Refraction is caused because light can speed up / slow down (and hence bend) depending on the medium it travels through The light ray bends towards the normal as it enters The light ray bends away from the normal as it leaves The ray entering the block is parallel to the ray leaving the block, if the block has parallel faces A ray entering the block at 90° is not refracted

Refraction

Water Try for yourselves the penny in the beaker trick… Water is denser than air, so light is refracted when it travels through the surface of the water This is why sticks seem to be bent if they are partly underwater, and why swimming pools look shallower than they really are Refraction lets you see objects that are normally hidden…

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 the 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

Pencil Your assessed task is to look at the pencil in the water, and explain why this is happening You will be assessed on: - –Your knowledge and understanding of light (and how it travels) –Your ability to explain ideas clearly

Leveling Level 4 - understanding that light travels in straight lines, but that the water causes it to bend (refract) Level 5 - explanation that refraction occurs when the light changes speed Level 6 - understanding that refraction occurs when the light slows down as it hits a more dense medium, and speeds up again when it enters a less dense medium (i.e. slow in water; faster again in air) Level 7 - explanation that the direction of the light will bend in different circumstances

Trick Questions