Waves Check your notes!

What is a wave? According to the “standards” it is A way for energy to be carried from one place to another without transferring the material. Please check your definitions: A mechanical wave is a disturbance that travels through a medium from one place to another. A disturbance can be a vibration or wiggle. A medium is a material: solid, liquid, or gas Please list 3 examples of mechanical waves

Anatomy of a Wave λ Crest is the top of a wave Trough is the bottom of a wave Equilibrium position is the resting position when there are no disturbances Amplitude is the magnitude of the disturbance from equilibrium A → the units depend on whether you’re talking about sound waves, water waves, or light wavelength is the distance between adjacent peaks or troughs in a wave λ → wavelength (m) λ crest A equilibrium position trough

Wavelength Practice Draw the wave below on your paper Count how many waves you drew Measure the amplitude Measure the wavelength of the wave

Frequency velocity is how fast the wave is moving v → velocity (m/s) frequency is the number of waves or oscillations each second. An oscillation is when something swings back and forth f → frequency units (1/s) or hertz (hz) If the 93 bus comes 10 times in an hour, what is the frequency? Example: If two waves pass by in 1 s then what is the frequency? v

Period period is the time it takes for one wave to pass or one oscillation. T → period units (s) Example: What is the period of a wave when you observe that two waves pass by in 1 s? The period (T) and frequency (f) are inversely related

Practice Problems In a large room, a sound wave traveling from a violin produces a tone with a frequency of 264 Hz. The speed of sound in the room is 340 m/s. What is the wavelength of the sound? The velocity of sound in a particular gas is 900 m/s. A sound wave propagating in the material has a wavelength of 15 m. What is the frequency of the sound?

The Wave Equation The velocity equation: v = fλ As the frequency increases, what happens to the wavelength? Velocity of a wave does not change when the frequency or wavelength changes Frequency Wavelength Velocity

Demonstration Let’s make some waves!

Mechanical Wave Types There are two types of mechanical waves: Transverse waves: when the particles in the wave moves perpendicular to the direction of the waves motion and energy transport. The wave moves forward slinky particles move up and down

slinky particles move back and forth Mechanical Wave Types Longitudinal waves: when the particles of the wave move parallel to the direction of motion and energy transport. The wave moves forward slinky particles move back and forth

Label each wave below as longitudinal or transverse and explain your choice Tsunami (giant wave of water) → _______________ Earthquake → _____________ Sound → ____________ Jump rope → _______________ Draw the waves A and B below in your notebook Which wave has a longer wavelength? Why? Which wave has a larger amplitude? Why? A B

Slinky Lab Purpose: to see how the velocity, frequency, and wavelength are related Hypothesis: answer the following in your notebook What do you think happens to the wavelength of a wave as the frequency increases or decreases? What do you think happens to the velocity of a wave as the frequency changes?

Procedures Make a table to record your data Create a wave using the slinky and record the following information for your wave # of swings in 10 s, you should calculate the frequency using this information Measure and record the wavelength Create a smaller wave and then repeat steps A and B above # of swings in 10 s frequency wavelength Wave 1 Wave 2

Frequency and Wavelength From your observations, how are the frequency and wavelength related? Fill in the table Frequency Wavelength ↓ ↑

Molecular Movement

Analysis Wavelength (m) Frequency (hz) Wave 1 Wave 2 Plot your data on two separate graphs. What does the area of your graph tell you? Look at the units!

The Wave Equation Frequency Wavelength Velocity Frequency Wavelength

Practice Classifying Waves

Waves Travelling in a Medium Why do we call them mechanical waves? How can we change a waves velocity faster? Do waves travel fastest in a gas, liquid, or solid? Do waves travel slowest in a gas, liquid, or solid?