Wave Motion and Sound Part 1 Wave Motion

Wave Motion and Sound

Part 1: Wave Motion

Which of the following is an example of a mechanical wave? Sound 2. Light 3. Microwaves 4. X-rays 1.

P 4. 4 A Ø Describe specific mechanical waves (eg on a demonstration spring, on the ocean) in terms of wavelength, frequency, speed and amplitude.

Wave Motion • A pulse is a single disturbance. • A wave is a series of pulses traveling through space. Pulse Wave: Picture shaking a slinky up and down

Wave Motion • Mechanical waves: need a medium (substance) through which to travel • Examples: water waves, slinky waves, sound waves • Electromagnetic waves: do not need a medium through which to travel • Examples: radio waves, microwaves, light, UV rays, x-rays

Which of the following is an example of a electromagnetic wave? Sound 2. Water 3. X-Rays 1.

Which of the following is an example of a mechanical wave? Sound 2. Light 3. Microwaves 4. X-rays 1.

Particle Motion • All waves can travel two different ways: • Transverse Wave: particles vibrate perpendicular to direction of traveling wave • Longitudinal Wave: particles vibrate parallel to direction of traveling wave

Video Ø Play Transverse vs. Longitudinal Video

Which type of wave does not need to travel through a medium? Electromagneti c 2. Mechanical 1.

Transverse Wave • • Crest: top point of wave (green dots) Trough: bottom point of wave (orange dots) Amplitude: distance from crest to x-axis Wavelength: length of one complete “cycle” crest trough

Transverse Wave • Frequency: number of “cycles” that pass per second • Can be number of crests, troughs, or wavelengths that pass per second • Symbol: f • Units: 1/seconds or Hertz crest trough

Transverse Wave Applet Ø Wave on a string Applet Ø Use the applet to change Amplitude and Frequency Ø Set to oscillate, no end, zero damping

1. 2. 3. 4. Which of the following is the wavelength of the wave pictured below? A B C D A D C B

1. 2. 3. 4. Which of the following is the amplitude of the wave pictured below? A B C D A D C B

Which of the following is the trough of the wave pictured below? 1. 2. 3. 4. A B C D A D C B

Which of the following is the crest of the wave pictured below? 1. 2. 3. 4. A B C D A D C B

P 4. 4 C Ø Compare and contrast transverse and compression (longitudinal) waves in terms of wavelength, amplitude and frequency.

• • Transverse Wave (Review) Crest: top point of wave (green dots) Trough: bottom point of wave (orange dots) Amplitude: distance from crest to x-axis Wavelength: length of one complete “cycle” crest trough

Compressional Waves • • • Compression: compressed area of wave Rarefaction: spread out area of wave Wavelength: length of one complete “cycle” of wave • measured from compression to compression • Frequency: number of cycles that pass per second Rarefaction

Longitudinal vs. Transverse

Which of the waves below has the larger wavelength? Wave A 2. Wave B 1. Wave B Wave A

Which of the waves below has the larger amplitude? Wave A 2. Wave B 1. Wave B Wave A Response Grid

Compression is to crest as rarefaction is to 1. 2. 3. 4. 5. Amplitude Frequency Wavelength Trough speed Response Grid

The number of wave crests per second is called 1. 2. 3. 4. Wavelength Frequency Speed amplitude Response Grid

P 4. 4 B Ø Identify everyday examples of transverse and compression (longitudinal waves)

Example: Longitudinal Wave • Sound is a longitudinal wave!! • When you speak, you vocal cords vibrate and “bump” the air particles close by. These particles then bump the next particle, etc. • If there were no air particles, there could be no propagation of sound!! • Is there sound in outer space? ?

EM Waves

Which of the following is NOT a transverse wave? 1. 2. 3. 4. Light Water Rope sound Response Grid