Practical 2

Demonstrate that light moves in a straight line and can be blocked by/ go through different types of materials using torch and laser. (Have students draw the light path)
Have students build periscope to demonstrate reflection of light. (Have students draw what they see with the periscope).
Teacher demonstrate of light refraction to “bend” a laser beam in water or in a plastic tube.

Equipment

Make x1 periscope

Teacher demonstrations of light refraction

Begin by demonstrating the way light passes through translucent/ transparent materials (eg glass, thin paper) and is absorbed by others (eg thick cloth).
Have students draw diagrams labelling materials and the path of the light.
Hold a discussion on how light moves in a straight line using a piece of opaque rubber tubing.
Have the students build a periscope to demonstrate how reflection can be used redirect light.
Have students draw a diagram of what they see through their periscope.

Periscope:

Create a cardboard prism (tape together two clean milk cartons with the tops cut off).
Cut a hole big enough to fit one mirror on one side of the carton
Cut a hole big enough to fit one mirror on the other end on the opposite side of the carton.
Insert the mirrors so they sit at a 45 degree angle facing each other, with the mirrored side facing the hole. Fix them in place with blu-tack.
Look through one end of the periscope. You should be able to see clearly out the other end. If not, re-adjust the mirrors.
Pick a spot in the classroom through the periscope and draw what you see using the periscope.

Demonstration:

Direct light through a plastic prism, adjusting the angle until the light is internally reflected through the prism.
Ask the students to discuss why the light no longer moves in a straight line. Remind them of how a straw appears bent in water.
Cut a small hole near the base of a two litre bottle.
Covering the hole, fill the bottle with water.
Point the laser through the bottle, directly at the hole.
Uncover the hole and allow the water to flow downwards into a bucket with the light directed at the hole.
Watch the light bend with the water into the bucket. (Best done in a darkened room).
Discuss how this is similar to the refraction and reflection of light in the prism.

Total cost: <$30.00

Match properties of transparent/ translucent/ opaque materials to how light interacts with them (worksheet)
What happens when a beam of light passes through air and into water?
Drawing diagrams of how the light moves.
List other methods of redirecting light that are used in life applications today.