Radiation of Light By the end of this lesson, you will be able to… Explain that light is emitted from luminous objects and is transferred by radiation Describe how light travels. Today’s Activities Concept Cartoon – Fireworks Demo – exploring ideas about light Explanation Re-visit the concept cartoon

I wonder why you always see the firework, before you hear the bang. Ooh aren’t those fireworks lovely!

A Light Investigation. Activity Prediction/ Observation Explanation Watch each of the light activities and fill in the table below. Each activity will have a set of questions for you to answer. Activity Prediction/ Observation Explanation Making shadows Holy Torch Changing Shadows Misty Light Light Sabre

Making Shadows Compare your shape to the shadow it makes. 1. On a piece of card, draw a shape and cut it out. 2. Put a piece of plasticene on the base of your shape and stick it upright on the bench. 3. Set up your ray box and shine it towards your shape. Place a mini white board behind your shape and draw the shadow that is made. Compare your shape to the shadow it makes. What do you notice? What does this tell you about how light travels

Holy Torch 1.Take a piece of scrap paper and punch some holes in it. 2. Roll it into a tube and tape it to the torch. Predict where the light will be seen when you switch the torch on. Did you predict correct? If yes, explain why?

Changing Shadows 1. Take the piece of card with the largest hole in it and place it closest to the bulb of the torch. 2.Now place the card with the next biggest hole behind it and repeat until all the cards are lined up. Predict how much light will be seen on the last piece of card. Why? Turn on the torch and check your prediction. What does this tell you about how light travels?

Misty Light Shine a torch along a black background. Your partner will then spray a fine mist over the path of light. Describe what you see. Why does this happen?

Light Sabre Bend the tube attached to the torch. Predict where the light will be seen when the torch is switched on. Test your prediction. Explain why this happens.

What is light? Light is produced by the Sun, and by other luminous objects such as light bulbs and matches. Light carries energy and travels as a wave and is transferred by radiation. Light waves travel in straight lines. Photo credit: © 2008 Jupiterimages Corporation

Faster than the speed of light…. Light travels at 300 000 000 m/s (300 million metres per second). The Sun is approximately 150 000 000 km from Earth (150 million kilometres). Therefore it takes 8 minutes for light from the Sun to reach Earth.

It’s because light travels faster than sound! So you hear the bang after you see the firework.