1. MANY PROPERITIES OF LIGHT CAN BE UNDERSTOOD USING A WAVE MODEL OF LIGHT

2. WATCHING WATER WAVES You do not need to visit the lake or ocean to make waves. In this activity, you can make waves right in your classroom. Fill a pie plate with water about 2 cm deep. Lightly tap the bottom of a pencil once in the middle of the surface of the water. Observe the waves that form. Lightly tap your pencil once per second on the surface of the water. Observe the spacing of the water waves. Increase the rate of your tapping. Observe the spacing of the water waves.

3. WATCHING WATER WAVES What did you find out? In what direction did the waves travel when you tapped the water lightly with your pencil? How did the spacing of the water waves change when the rate of tapping increased? Dump the water in a sink and return the pie plates to me.

4. PROPERTIES OF WAVES A wave is a movement that transfers energy through matter or space. Energy is the ability to apply a push or pull on an object. Examples: Water wave moves energy through water. Sound wave moves energy through air. Radio wave moves energy through space. It is helpful to use water waves to describe waves in general. You cannot see many other kinds waves. Important: A water wave does not carry water along with it. Only energy carried by the water wave moves forward. A duck moves up and down as a wave passes – it does not move forward.

5. FEATURES OF WAVES Complete the following handout and label and describe the parts of a wave: Crest – The highest point in the wave. Trough – The lowest point in the wave. Rest position – Where the water would be if it were still. Wavelength – The distance from crest to crest or from trough to trough. It is usually measured in meters. Amplitude – The height of a wave crest or depth of a wave trough as measured from its rest position. It is related to the amount of energy carried by the wave. Frequency – The number of repetitive motions that occur in a given time. It is usually measured in hertz (Hz), or cycles per second.

6. FREQUENCY FORMULA In this activity, you can calculate frequency by using the number of cycles, the time and an equation. Use the following equation to calculate the frequency (in hertz) for each question below: Frequency = cycles ÷ seconds Remember: What must be done with the time unit before dividing?

7. FREQUENCY FORMULA (CONTINUED) a.Pendulum: 24 swings in 6 seconds b.Merry-go-round: 12 revolutions per 2 minutes c.Flashing red light at an intersection: 30 flashes in 0.5 minutes d.Heart rate: 18 beats per 20 seconds e.Car drive shaft: 2000 revolutions per minute

8. TWO TYPES OF WAVES The matter a wave travels through is called a medium. The medium can be a solid, liquid or gas. For sound waves the medium is air and for ocean waves the medium is water. The two types of waves that travel through a medium are: transverse waves compression waves.

9. TRANSVERSE WAVES Matter in the medium moves up and down perpendicular to the direction that the wave travels.

10. COMPRESSION WAVES Matter in the medium moves back and forth along the same direction that the wave travels.