{{ :light:banner-light-st3-790x50.jpg |Light ST3 Banner}} ====== LIGHT - Travel & Reflection ====== === OUTCOMES: === Students gather evidence to support their predictions about **how light travels and is reflected** === Students learn: === |SCIENCE |Identify scientific principles underlying bhaviour of light| |TECHNOLOGY |Record and analyse data| |ART |Blended multimedia elements | |ENGINEERING |Design, build and test experimental device(s) | |MATHEMATICS |Use comparative data to differentiate materials| ====== REVISION: ====== === Reflection: === Like a rubber ball, light bounces off most things it hits - **Light is made up of lots of things that bounce.** - When light falls on something, mostly, it is **like a hand-full of rubber balls** being thrown - not just one ball. - When light travels to something **opaque**, some of this light stops there - BUT, some of this light bounces off. - When light travels to something **translucent or transparent**, most of the light passes through - BUT, some of this light bounces off. - When **light bounces off things and travels to your eyes**, this information is passed to your brain and you are able to see. ((Blecha, Gega, & Green, 1979, p. 154)) 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 **[[http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/waves/generalwavesrev7.shtml|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 - **[[http://www.lightandmatter.com/html_books/7cp/ch07/ch07.html|detailed science resources from lightandmatter - Read more...]]** {{ :learn:light:sun-duck-rays-640x180.jpg?640x180 |Light Travels from the sun & objects}} === Fig 1. Two Ray Diagrams: How Light Travels From The Sun & From Objects === If you need more help, check out the on-line **How We See Things** interactive (lower down this page) about //reflection// and //refraction// ---- **WARNING: NEVER LOOK INTO THE SUN, OR A LASER OR ANY OTHER BRIGHT LIGHT** ---- ====== LOOPY NIGHT-LIGHT EXPERIMENT ====== === MATERIALS: === 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. === PROCEDURE: === 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 === OBSERVATIONS: === * Student should record each change that they make and include a rough sketch of each layout === RESULTS: === - Each student must draw and label one diagram of any of the layouts that were completed by their group. - 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) - What principles of light transmission were used: reflection, refraction and/or other? - Is there a better way to send light around in a loop? === DISCUSSION: === - If repeating the experiment, would you do things differently - Do you know of any measuring device where measurements depend on light travelling in a loop? Write down your answers. ==== Example - How Light Travels (BBC interactive experiments & results): ==== 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. === Light & Dark: === [[http://www.bbc.co.uk/schools/scienceclips/ages/5_6/light_dark.shtml|{{ :learn:light:stage3-2016:ligh-up-things-640x360.jpg |Light things up}}]] **1.** [[http://www.bbc.co.uk/schools/scienceclips/ages/5_6/light_dark.shtml|Light & Dark]] - Light & Dark: Drag different things into the centre of a dark room: |1. Does the candle shine the same amount of light as the torch? | | |2. Does the candle shine the same amount of light everywhere in the room? | | |3. Does the torch shine the same amount of light everywhere in the room? | | ---- === How We See Things: === [[http://www.bbc.co.uk/schools/scienceclips/ages/10_11/see_things.shtml|{{ :learn:light:bbc-how-we-see-640x360.jpg?640x360 |BBC How we see things}}]] **3.** [[http://www.bbc.co.uk/schools/scienceclips/ages/10_11/see_things.shtml|How We See Things - Drag different angled mirrors into the path of the light:]] ^Follow the instructions: ^Enter your answer below: ^ |1. What happens when you drag a mirror onto the light (drag first, then click)? | | |2. Can you select the correct mirror to reflect & re-direct the light beam onto the tent? | | |3. How many mirrors do you need to direct the light beam onto the bench?| | |4. Can you direct the beam onto the dog & then the bench by only changing one mirror? | | |5. How many mirrors do you need to direct the light beam onto the balloon stall?| | |6. Press the 'QUIZ' button. How many answers can you get right?| | ---- === Refraction === 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