Students gather evidence to support their predictions about how light travels and is reflected

Like a rubber ball, light bounces off most things it hits - Light is made up of lots of things that bounce.

1. When light falls on something, mostly, it is like a hand-full of rubber balls being thrown - not just one ball.
2. When light travels to something opaque, some of this light stops there - BUT, some of this light bounces off.
3. When light travels to something translucent or transparent, most of the light passes through - BUT, some of this light bounces off.
4. When light bounces off things and travels to your eyes, this information is passed to your brain and you are able to see. ¹⁾

When light bounces off of things, scientists call this reflection

To explain how light travels and bounces off of things, scientists use 'ray diagrams'.

A ray diagram is a drawing with arrows that shows where the light is coming from, what it is hitting, and where it travels after it bounces off of something - detailed science resources from lightandmatter - Read more...

If you need more help, check out the on-line How We See Things interactive (lower down this page) about reflection and refraction

Example materials list - One of each item is required for each student group (say each 4-5 students):

• A cheap LED torch (or similar $2 - $5 light source) for each group
• A light-activated 'night-light' or similar device that turns on/off in the presence/absence of light (available for around $8 - $10 each - One can be shared by multiple groups if necessary).
• A light 'baffle' - A square, opaque dividing strip that is 300mm hight x 300mm long and less that 150mm deep (for example, a 300mm square cut from the side of a thick/corrugated cardboard card-board box or similar)
• Any small (150mm x 150mm or larger) mirror (see below - used only for testing purposes).
• Scissors and glue/tape available for each group for cutting/gluing the A4 paper sheet. The A4 sheet should be standard white photo-copy/printer paper, but any other, additional colours can be used.
• Ideally, students should work in a shaded area where their night-light is turned away from any windows/doors or other sources of bright/reflected light.
• A computer or similar device connected to Internet for access to on-line interactives
• Google sheet or science journal to record results

Make a guess (your 'hypothesis') how you will design and build an optical device to make the light from the torch loop around and turn the night-light on/off.

SAFETY WARNING: Students MUST NOT look directly into the torch/light at ANY time.

Before commencing the task, the student and teacher must discuss and agree about SAFE ways how to test whether the light is travelling in a loop!

When the teacher is confident that students understand and will comply with the safety rules:

• Each group must place their night-light and a torch parallel to each-other so that no light from the torch can fall on the night-light.
• In addition, the square cardboard (or similar) 'baffle' should be placed vertically between the night-light and torch to ensure there is no 'short circuit' for light to travel between the torch and the night-light.
• Students must design a device using only one sheet of A4 paper to reflect or reflect sufficient light to turn the night-light on/off.
• The teacher should use a mirror placed at the end of the baffle to reflect light back and prove that the sytem will work using light reflected back to the night-light from the torch.
• Students must be able to show that the light is travelling from the torch, around the full length of the baffle, and then back to the night-light.
• Any solution to short-circuit the path around the full length

• Student should record each change that they make and include a rough sketch of each layout

1. Each student must draw and label one diagram of any of the layouts that were completed by their group.
2. Each student must create a 'ray diagram' showing how the light travels around the loop for the layout that they have chosen in item #1 above (the previous item)
3. What principles of light transmission were used: reflection, refraction and/or other?
4. Is there a better way to send light around in a loop?

1. If repeating the experiment, would you do things differently
2. Do you know of any measuring device where measurements depend on light travelling in a loop?

Write down your answers.

In your class/group discussions, describe some everyday situations where, how and why people, plants and animals use light and shadow.

Complete the on-line interactive tasks to predict, observe and record the effects of shining light on a variety of everyday objects.

1. Light & Dark - Light & Dark: Drag different things into the centre of a dark room:

3. How We See Things - Drag different angled mirrors into the path of the light:

https://www.youtube.com/watch?v=8RM46yvDOHI

BBC Interactive - http://www.physicsclassroom.com/PhysicsClassroom/media/interactive/Refraction/index.html Block - http://www.freezeray.com/flashFiles/Refraction1.htm