Chapter 14

Define vibration. ◦ “wiggle” in time; bell chimes Define wave. ◦ “wiggle” in time and space ◦ or a disturbance moves through a medium; it’s not matter moving through a medium, it’s energy

Define electromagnetic waves. ◦ Transmission from one place to another does not require a material medium ◦ Ex: light, radio waves, infrared (IR), ultraviolet (UV), x-rays, gamma rays and microwaves Define mechanical waves. ◦ Requires a material medium; ◦ springs, slinkies, sound waves

Crest Trough Wavelength Amplitude

Define period. ◦ (T) time between passage of two successive crests (seconds) Define wavelength. ◦ ( ) distance from the top of one crest to the next (or any successive identical parts of the wave) (meters)

Define frequency. ◦ (f) how often a vibration occurs; ◦ the number of crests (or troughs) passing a given point in a certain time ◦ measured in Hertz (Hz) = 1cycle/second 1 = s -1 =Hz second Equations: f = 1 and T = 1 T f

Define wave speed (velocity). ◦ how fast the energy moves from one place to another Equations: v = f velocity = wavelength * frequency m/s = ( m ) (Hz) m/s = ( m ) (1/sec )

Define transverse wave. Motion of the medium is perpendicular (at right angles) to the direction the wave travels energy Particle in the medium

Define longitudinal wave. Motion of the medium is parallel (in the same direction) to the direction the wave travels Another name for a longitudinal wave is a compressional wave. Particles in the medium energy

Waves with larger amplitudes have more energy. Medium (plural “media”) ◦ Substance the wave moves through ◦ Can be solid, liquid, or gas ◦ EX: listen for the train, hear your own voice different Low amplitude Low energy High amplitude High energy Same wavelength

When a wave moves from one medium to another... v = f Medium #1 to Medium #2 Frequency Wave Speed Wavelength same changes

Label the diagram below. Incident wave Transmitted wave Reflected wave

When a wave moves... from a less dense to a more dense medium the transmitted wave is inverted These two waves are said to be out of phase.

When a wave moves... from a more dense to a less dense medium the transmitted wave is upright These two waves are said to be in phase.

When there is a large difference in density most of the energy (wave) is reflected. When there is a small difference in density most of the energy (wave) is transmitted.

Tools in our Physics Toolkit Problem Solving... 5 stepsALWAYS SHOW YOUR WORK!!! 1. Knowns 2. Unknowns 3. Equations (just variables) 4. Work-equation with numbers plugged in 5. Answer with units and correct sig-figs (State the problem) (Gather information) (Form a hypothesis) (Test the hypothesis) Analyze data Draw Conclusions

Example Problem page 91 What is given in the problem? Knowns: m = 1500 kg a = m/s 2 What are we trying to find? Unknown: F = ? Which equation has those variables in it? Equation: F = ma Solve for the unknown variable: Plug in the values and solve: Work: F = (1500 kg)(+3.00 m/s 2 ) State your answer with unit and correct sig figs.: Answer: F = 4500 N

Homework: Wave Motion WS Be sure to show your work. Every number needs units AND correct significant figures!