# Waves How many waves can you identify You

• Slides: 28

Waves

How many waves can you identify? • You have just returned home from a day at the beach. You are hungry from playing in the ocean under the hot sun. You microwave some left over pizza. The phone rings, and you turn on the radio. • List all the waves in your new packet p 2.

What is a wave? • A wave is a disturbance that transmits energy through matter or space. • A medium is a substance or material which carries the wave.

P 3 Packet • What is the difference between a mechanical wave and an electromagnetic wave?

Energetic Waves • Tie a rope to the back of your chair. Hold the other end so that it is almost straight but not tight. • Move the rope up and down quickly to create a single wave. Record your observations on the left side of your INB. • Which direction does the wave move? • Compare the movement of the rope with the movement of the wave. • Where does the energy come from?

Put a piece of tape on the rope • What direction does the tape move? Is it in the same direction as the wave? Observe in INB • Energy can be carried from its source by a wave. But the material does not move with the energy. • Ex leaf on water, sound in air. • Which direction does the wave move? • Compare the movement of the tape with the movement of the rope with the movement of the wave. • Where does the energy come from?

Do Now • How are light and sound alike? How are they different? Use your Nature of Waves packet to help you. • On 2 pages (p 4) of your packet, make a gigantic Venn diagram comparing the two. Light Sound

Two kinds of waves • Longitudinal • Transverse Read Types of Waves, p 6 -9, highlight 3 of the most important things for each type of wave.

Longitudinal • Vibrates parallel to (in the same direction of) wave travel – The “LONG” way – For example: sound waves Animation courtesy of Dr. Dan Russell, Kettering University – The other end of the medium moves without the actual movement of matter.

Animation courtesy of Dr. Dan Russell, Kettering University

Longitudinal • Use your Slinky to demonstrate a longitudinal wave: – Work with a partner – Stretch it out along the table – One of you grasp and draw several coils of a stretched Slinky toward yourself – Release the coils – The other student must hold his or her end of the Slinky still – A longitudinal wave pulse will be generated and travel down the length of the Slinky.

Longitudinal • Are composed of – Compressions, where the parts of the medium (coils of the Slinky) are closer together than normal – In this investigation, you created (generated) compressional longitudinal waves – The waves traveled through a media (the slinky)

Longitudinal • Use your Slinky to demonstrate a longitudinal wave: Work with a partner Stretch it out along the table One of you stretch a segment of the Slinky Release the coils The other student must hold his or her end of the Slinky still – A longitudinal wave pulse will be generated and travel down the length of the Slinky. – – –

Longitudinal • Are composed of – Rarefactions, where the parts of the medium are farther apart than normal – In this demonstration, you created (generated) rarefactional longitudinal waves – The waves traveled through a media (the slinky)

Transverse • Vibrates perpendicular (at right angles) to the wave travel – An example of transverse waves are Electromagnetic waves. Trans means across. Animation courtesy of Dr. Dan Russell, Kettering University

Transverse • Use your Slinky to demonstrate a transverse wave: – Work with a partner – One of you move your end of the Slinky back and forth (left and right, like a snake crawling), perpendicular to its stretched length. – The other student must hold his or her end of the Slinky still – A series of transverse waves will be generated and will travel through a medium (Slinky)

Reflection • Complete your Venn diagram comparing transverse waves and longitudinal waves.

Electromagnetic Waves • Are waves which are capable of transmitting its energy through a vacuum (i. e. , empty space) • Produced by the vibration of electrons within atoms on the Sun's surface • Travel through space until they reach Earth • Examples are light and heat • Are transverse waves which mean the particles vibrate ACROSS the direction of the wave

Mechanical Waves • Are not capable of transmitting their energy through a vacuum (space) • Require a medium in order to transport their energy from one location to another Sound waves are mechanical longitudinal.

Mechanical Waves • Waves traveling through a solid medium can be either transverse waves or longitudinal waves.

Water Waves • A combination of longitudinal & transverse Animation courtesy of Dr. Dan Russell, Kettering University

DO NOW Sometimes people at a sports event do “the wave”. Do you think this is a real example of a wave? Why or why not? Quick Write on p 2.

Parts of a Wave

Read and Learn Read the Nature of Waves handout p 10 -12 and define wavelength, amplitude, and frequency in your notes on p 5 of packet. Crest, trough and rest position are also important terms. • www. scilinks. org HSTP 480, HST 490

Parts of a Wave 1. Wavelength – 1. In transverse waves – distance between two crests or troughs 2. In longitudinal waves – distance between two compressions or rarefactions 2. Frequency – the number of waves that pass a point in one second 1. Long wavelengths have low frequencies 2. Short wavelengths have high frequencies 3. Amplitude (wave height) – the distance from the middle of a transverse wave to the crest or trough

Change amplitude! • Hold a slinky on the floor between you and your partner. Move one end from side to side at a constant rate. The number of times you move it from side to side is (back and forth) each second is the frequency. • Keeping the frequency the same, increase the amplitude. How did the change in amplitude affect the wavelength? Record in packet.

Change frequency! • Now shake the slinky back and forth twice as fast (double the frequency). • What happened to the wavelength? • Record in packet.

Summary • Write 3 sentences showing how each property changes the other: use the terms frequency, amplitude and wavelength.