12.3 Properties of Wavespp. 452 -458

Mr. Richter

Agenda

Warm-Up

Review HW

Notes: Types of Waves Wave Speed Waves and Energy

Objectives: We Will Be Able To…

Distinguish local particle vibrations from overall wave motion.

Differentiate between types of waves.

Apply the relationship among wave speed, frequency, and wavelength to solve problems.

Relate energy to amplitude.

Warm-Up:

How does sound travel from your mouth to a person’s ear?

Can you make sound travel faster?

Louder?

Types of Waves

Mechanical vs. Non-Mechanical Waves

Mechanical wave: a wave that propagates through a deformable, elastic medium medium: the material through which a disturbance

travels

Non-mechanical waves: do not require a medium through which to pass X rays, magnetic waves, visible light, radio waves, etc.

Pulse vs. Periodic Waves

Periodic wave: whenever the source of the wave’s motion is a periodic motion (repeated), a periodic wave is produced.

Pulse wave: a wave consisting of a single traveling pulse.

Transverse and Longitudinal Waves

Transverse Waves

Particles of the medium move perpendicularly to the wave motion

For example: wave travels to the right as the particles of the Slinky move up and down.

https://www.youtube.com/watch?v=UHcse1jJAto

Longitudinal Waves

when the particles of a medium vibrate parallel to the direction of the wave

also called a density wave or pressure wave

https://www.youtube.com/watch?v=aguCWnbRETU

Transverse and Longtudinal Waves

https://www.youtube.com/watch?v=Rbuhdo0AZDU

Wave Speed

Wave Speed

The speed of propagation of a mechanical wave depends on the medium through which the wave travels. Some media are thicker or less flexible than

others. Think of sound traveling through water as

opposed to traveling through air.

Speed of propagation of a mechanical wave is constant for any given medium. Example: the speed of sound in air is always

(roughly) 340 m/s.

Wave Speed

A wavelength is the displacement of a wave in one period of time. (How long is the wave for a complete cycle.)

If frequency is increased, wavelength must decrease.

Your Turn

The piano string tuned to middle C vibrates with a frequency of 264 Hz. Assuming the speed of sound in air is 343 m/s, find the wavelength of the sound waves produced by the string.

v = ƒλ

343 m/s = 264 Hz * λ

λ=343/264 = 1.30 m

Waves and Energy

Waves and Energy

Energy transfers from adjacent particles across the medium.

Waves transfer the motion of matter without transferring the matter itself. This often makes waves a

more efficient method to transfer energy.

The larger the amplitude, the greater the energy transferred.

Wave Energy Commercial

Wave Energy

Wrap-Up: Did we meet our objectives?

Distinguish local particle vibrations from overall wave motion.

Differentiate between types of waves.

Apply the relationship among wave speed, frequency, and wavelength to solve problems.

Relate energy to amplitude.

Homework

p. 470 #24-28, 35