1. Shadows Shadows are places where light is “blocked”: Rays of light

2. Luminous and non-luminous objects A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objectsReflectors

3. We see things because they reflect light into our eyes: Homework

4. Reflection Reflection from a mirror: Incident ray Normal Reflected ray Angle of incidence Angle of reflection Mirror

5. The Law of ReflectionThe Law of Reflection Angle of incidence = Angle of reflection In other words, light gets reflected from a surface at ____ _____ angle it hits it. The same !!!

6. Clear vs. Diffuse Reflection Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions

7. Using mirrors Two examples: 1) A periscope 2) A car headlight

8. Refraction Refraction is when waves ____ __ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pencil is placed in water it looks like this: In this case the light rays are slowed down by the water and are _____, causing the pencil to look odd. The two mediums in this example are ______ and _______. Words – speed up, water, air, bent, medium

9. Refraction through a glass block: Wave slows down and bends towards the normal due to entering a more dense medium Wave speeds up and bends away from the normal due to entering a less dense medium Wave slows down but is not bent, due to entering along the normal

10. Examples of Refraction Is the fish deeper or shallower than its image appears to be? Should you stab above or below the image of the fish to spear it?

11. Examples of Refraction Explain why: You can’t see the coin in the cup without water You can see the coin in the cup with water

12. Speed of sound The speed of sound in air is around 330 m/s. What happens when sound travels through different materials? Material Speed of sound (in m/s) Conclusion – the denser the material, the faster sound travels through it

13. Making Sounds A sound is made when an object or material VIBRATES. Take, for example, a guitar. To make a sound with a guitar a string has to vibrate. We can raise the pitch of the sound a guitar makes by doing three things: 1) _________ the length of the string 2) _________ the string 3) Using a _________ string We can make the sound louder by ________ the string harder Words – tightening, thinner, increasing, plucking

14. Using an oscilloscope 1) Quiet sound, low frequency: 2) Quiet sound, high frequency: 3) Loud sound, low frequency: 4) Loud sound, high frequency:

15. How sound travels… As we know, sound waves are formed when something vibrates. But how does the sound reach our ears? 1) An object makes a sound by vibrating 2) The vibrations pass through air by making air molecules vibrate 3) These vibrations are picked up by the ear Air molecules

16. How does the ear work? 1) Sound waves are “funnelled” into the ear by the pinna 4) These vibrations are turned into electrical signals in the cochlea 2) These vibrations make the ear drum vibrate 3) These vibrations make the ear bones vibrate 5) The electrical signals are then sent to the brain

17. The Eye Read the definitions on the next slide, then label the eye anatomy diagram below.

18. The Eye Definitions Cornea - the clear, dome-shaped tissue covering the front of the eye. Iris - the colored part of the eye - it controls the amount of light that enters the eye by changing the size of the pupil Lens - a crystalline structure located just behind the iris - it focuses light onto the retina Optic nerve - the nerve that transmits electrical impulses from the retina to the brain Pupil - the opening in the center of the iris- it changes size as the amount of light changes (the more light, the smaller the hole) Retina - sensory tissue that lines the back of the eye. It contains millions of photoreceptors (rods and cones) that convert light rays into electrical impulses that are relayed to the brain via the optic nerve Vitreous - a thick, transparent liquid that fills the center of the eye - it is mostly water and gives the eye its form and shape (also called the vitreous humor )

19. Light Waves Light energy travels in the form of a transverse wave. Below is a picture of a light wave

20. Sound Waves Sound energy travels in the form of a longitudinal wave. Below is a picture of a longitudinal wave travelling along a spring.

21. Sound Waves When a longitudinal wave moves through a material, the particles of the material move backwards and forwards along the direction in which the wave is travelling.