Brain Pop http://www.brainpop.com/science/energy/waves/

Waves A wave is a disturbance that transfers energy through space or matter Energy moves; matter does NOT A medium is the material through which a wave travels Some waves need a medium, some do not

Mechanical waves require a medium Examples: sound, water waves, seismic waves (earthquake) Electromagnetic waves do NOT require a medium Examples: light, microwaves, radio waves

Two types of waves: Transverse waves – particles of medium vibrate perpendicular to direction of wave motion

Parts of a transverse wave: Crest – highest point of a wave Trough – lowest point Wavelength – distance from crest to crest, or trough – trough Amplitude – distance from rest to crest Draw and label:

Longitudinal wave – particles of medium vibrate parallel to wave motion

Compressions – areas of increased density Rarefactions – areas of decreased density

All waves have 4 properties: Wavelength measured in meters (m) Shorter wavelength = more energy Amplitude measured in meters (m) Higher amplitude = more energy Frequency measured in hertz (s-1, or 1/s) – # of wavelengths that pass in a given second Higher frequency = more energy Speed = wavelength x frequency ; measured in meters/second

As wavelength increases, frequency decreases

Check Your Understanding As the wavelength of a wave in a uniform medium increases, its speed will _____. a. decrease b. increase c. remain the same

Wave Speed… 1. If speed is measured in distance per time, which properties of waves do you think we can use to calculate wave speed? Wavelength and frequency because they measure distance and time

Think back to our lab… What affected how fast the slinky went? Amplitude? Wavelength? Frequency? The medium?

Check Your Understanding As the wavelength of a wave in a uniform medium increases, its frequency will _____. a. decrease b. increase c. remain the same

Wave Speed… 3. What do you think affects how fast waves travel? The properties of the medium (not the wave!) affect how fast waves travel (if they’re solid, liquid, or gas; how dense they are; their temperature; etc)

Calculating Wave Speed The “wave equation” is: Where v = ________________________ ƒ = ________________________ λ = ________________________ V = ƒ λ Wave speed or velocity in m/s Frequency in wave/sec or Hz Wavelength in meters (m)

Calculating Wave Speed In the ocean, a wave has a wavelength of 4 m and a frequency of 2 Hz. What is the wave’s speed?

Calculating Wave Speed Josh sings a high note, which results in a sound wave with a frequency of 512 Hz and a wavelength of 0.66 m. What is the speed of sound?

Calculating Wave Speed A wave is traveling at a speed of 12 m/s and its wavelength is 3 m. What is the wave frequency?

Calculating Wave Speed A wave is traveling at a speed of 18 m/s with a frequency of 3 Hz. A second wave is traveling at a speed of 16 m/s with a frequency of 4 Hz. What is the difference between these two wavelengths?

Medium Wavelength Frequency Speed Stan and Anna are conducting a slinky experiment. They are studying the possible affect of several variables upon the speed of a wave in a slinky. Their data table is shown below. Fill in the blanks in the table, analyze the data, and answer the following questions. Medium Wavelength Frequency Speed Zinc, 1-in. coils 1.75 m 2.0 Hz ______ Zinc, 1-in. coils 0.90 m 3.9 Hz ______

Back to your labs Look back at the wavelength column in your labs. Calculate the wavelength for each of the tuning forks

Buzzer Beater – Wave Properties and Speed Without your notes. Label the properties of the wave below. Then, explain what each property is and the units we use to measure it (if applicable) Wavelength – Frequency – Wave Speed – Amplitude – A wave is traveling at a speed of 24 m/s and its wavelength is 8 m. What is the wave frequency?