Light Seeing objects Reflection Refraction Speed of light Colours

Seeing Objects 1 When you are reading a book, how do you actually see the book? Light strikes the book and ________ into your eye. What other objects are seen by _________________? Planets People’s faces Trees

Seeing Objects 2 When you look at the Sun, how do you actually see it? NEVER LOOK DIRECTLY AT THE SUN! Light is ________ by the Sun and travels straight into your eye. What other objects are seen by ________? We call these objects ______________. Glow-worms Light bulbs Stars Torches Fires Fireworks are light sources

Exercise 1: Seeing Objects Light is a type of ______. Our eyes are able to detect light. There are two different ways we see objects. We see some objects by _______ light. For example: a planet or a book. We call these objects ____________. We see some objects because they emit light. For example: the ____ and a light bulb. We call these objects ________. reflected luminous Sun energy non-luminous

Exercise 2: Work in Pairs to Decide Which Sentences Below Are Correct. 1. Light is a type of force. 2. Light is a type of energy. 3. Sound travels faster than light. 4. Light travels faster than sound. 5. Light travels faster than the fastest car. 6. Light can bend around corners. 7. Light travels in zigzags. 8. Light travels in straight lines. 9. Luminous objects are seen by reflected light. 10. Luminous objects emit their own light.

Exercise 3: Light for Communication Light can be used to communicate information in numerous ways, can you think of any? Try to complete the boxes below with your ideas. Hint! Think OLD and NEW.

Light Light travels in ___________. How do we know? 1. You can _________________. 2. __________ are formed. A shadow is just a _________ an object where light ___________. Shadow region

Reflections If you shine a ____ of light (a ray is a ________________) at a plane mirror, what do you observe? The angle the ray of light strikes the mirror at is the same as the angle it leaves the mirror. Incident ray Reflected ray Normal Angle of incidence = Angle of reflection

Exercise 4: Light 1. What is a shadow? 2. How do we know light travels in straight lines? 3. What is a ray of light? 4. In light diagrams, what is the normal? 5. If a ray of light strikes a plane mirror at 37° at what angle will it be reflected? 6. What is lateral inversion?

Exercise 5: Reflections 1 Which diagram correctly shows how a ray of light would be reflected by a plane mirror? 1. 2. 3.

Exercise 6: Reflections 2 Which diagram incorrectly shows how a ray of light would be reflected by a plane mirror? 1. 2. 3.

Investigating Mirrors 2 1. Position two mirrors as shown on the left. 2. Shine a ray of light at mirror A. A. 3. Vary the angle at which light strikes mirror A. 4. What do you observe? 5. What do you observe when light strikes mirror A as shown? 6. When mirrors are arranged like this we can make an instrument. What is the instrument called? B.

Exercise 7: Two Mirrors 1. Complete the diagram below to show the path of light as it strikes the mirrors. 2. What do we call this device? 3. Give two uses of this device. 4. At what angle should the mirrors be?

Investigating Light 1. Place a block of Perspex on a piece of paper and draw around the block. 2. Shine a ray of light at the Perspex block and mark it on the paper. 3. Mark on the path of the light ray through the glass block. As the ray of light enters the Perspex block it __________ DIRECTION. When the ray of light leaves the Perspex block it CHANGES DIRECTION ________. This effect is called ____________. 4. Mark on the path of the light ray as it leaves the block. 5. What do you observe?

Refraction When a light ray is incident upon a Perspex block; several things happen. Incident ray Normal The light ray also ________________. This is called ___________. The light ray _______ TOWARDS _________ inside the block. Refracted ray When the light ray leaves the Perspex it _______ AGAIN and is __________ AWAY FROM THE ________. Emergent ray

Exercise 8: Complete the Diagrams Below for Light Entering a Perspex Block

Density and Refraction DENSITY is the property of a material which tells us HOW MANY PARTICLES are in a CERTAIN ______. Example: LIQUID WATER is _______ DENSE than WATER ________. When a light ray moves from a LESS _______ MEDIUM to a MORE ________ MEDIUM it SLOWS DOWN and REFRACTS __________ THE NORMAL. When a light ray moves from a MORE DENSE MEDIUM to a LESS DENSE MEDIUM it ________ and REFRACTS _________ FROM THE NORMAL. Air (Less dense) Perspex/Glass/Water (More dense) Air (Less dense)

Speed of Light Which is the fastest - LIGHT or SOUND? HINT! Think about THUNDER and LIGHTNING. Light travels a lot faster than sound! Examples During a thunder storm you SEE the _______ BEFORE you ______ the _______. If you are at the far end of a field and a starting pistol is fired at the other end, YOU SEE THE PUFF OF SMOKE BEFORE YOU HEAR THE BANG.