WAVE IF YOU GET IT  Before you start collecting data:  What questions must your team answer about your model(s)?  Has your model(s) been designed in a way that you can collect and communicate evidence to demonstrate wave energy?

Introduction to Waves November, 2015 COPY TODAY ’ S HOME LEARNING INTO YOUR AGENDA START A NEW PAGE OF CORNELL NOTES TITLE THE PAGE WITH THE HEADING SHOWN ABOVE FQ: WHAT ARE THE PROPERTIES OF WAVES?

Waves & Energy  Energy – the ability to do work Wave Wave – a disturbance that transfers ENERGY from place to place

What carries Waves? Medium – the material through which a wave travels Medium – the material through which a wave travels gases (air) gases (air) liquids (water) liquids (water) solids (rope) solids (rope) Mechanical wave: waves that require a medium through which to travel Mechanical wave: waves that require a medium through which to travel What about outer space? What about outer space?

Not all waves are mechanical Energy that travels through space: light Energy that travels through space: light Not mechanical, but electromagnetic (more on this later) Not mechanical, but electromagnetic (more on this later)

Do waves carry the medium with them? Does the ping-pong ball “ ride ” the wave? Does the ping-pong ball “ ride ” the wave? Consider: the medium is made of particles The medium vibrates – moves in a repeated back-and-forth or up-and-down motion The medium vibrates – moves in a repeated back-and-forth or up-and-down motion

Types of Waves  Rope Slinky Slinky Write down 3 things you notice about each picture. Write down 3 things you notice about each picture.

Types of Waves - Transverse  Rope –Moves up & down or side-to-side –Wave moves medium at right angle to direction waves travel

Types of Waves - Longitudinal Moves the medium parallel to the direction the waves travel

Properties of Waves

1. Amplitude Amplitude is distance particles move away from equilibrium (rest) More ENERGY = greater amplitude AmplitudeWavelength

Amplitude measured…. PRESSURE Distance away

2. Wavelength Wavelength is the distance between repeats (crest to crest, trough to trough, compression to compression, or rarefaction to rarefaction) AmplitudeWavelength

Properties of Waves

3. Frequency Frequency- number of vibrations (waves) in a certain amount of time. In one second the unit= Hertz (Hz)

Properties of Waves

See lightning before you hear thunder Speed of light = 186,000 miles per second Speed of light = 1,000,000 faster than sound Speed formulas:  Speed = distance/time (v = d/t)  Speed = wavelength * frequency (v = λf)  Frequency = speed/wavelength (f = v/λ)  Wavelength = speed/frequency (λ = v/f) 4. Speed (v)

Q: The speed of a wave on a rope is 50cm/s and its wavelength is 10cm. What is the wave ’ s frequency? (How many crests will pass a certain point every second?) Speed = wavelength x frequency Frequency = speed/wavelength f = (50 cm/s)/(10 cm) f = 5/s f = 5 Hz

Q: Which wave property is directly related to energy? A: Amplitude The greater the energy, the greater the amplitude

Q: Which wave properties are distances? A: Wavelength = distance between two corresponding parts of a wave A: Amplitude = maximum distance the particles of the medium carrying the wave move away from their rest positions

Q: Which wave properties are measured relative to time? A: Speed = distance/time A: Frequency = number of waves that pass a given point in a certain amount of time

Q: Two waves have the same wavelength and frequency. How do their speeds compare? (Which is greater, or are they the same?) (Which is greater, or are they the same?) Remember: Speed = wavelength x frequency A: If wavelength and frequency are equal, speeds are equal

Q: A wave ’ s frequency is 2 Hz and its wavelength is 4 m. What is its speed? Remember: Speed = wavelength x frequency Answer: Speed = 4 m x 2 Hz Speed = 4 m x 2 /s Speed = 8 m/s

Q: A wave travels at 3 m/s along a spring toy. If the wavelength is 0.2 m, what is the wave ’ s frequency? Speed = wavelength x frequency Frequency = speed/wavelength Answer: f = (3 m/s)/(0.2 m) f = 15 /s f = 15 Hz

How does your voice work? What happens when you make your voice higher or lower? What happens when you make your voice higher or lower? Does bumping into matter affect a sound wave? Does bumping into matter affect a sound wave? How can you change the straw to change the waves of sound energy? How can you change the straw to change the waves of sound energy?

White boards ready!  Which type of wave does NOT require a medium on which to travel?  Which type of wave DOES require a medium on which to travel?  What are the two types of mechanical waves?  Draw and label a transverse wave.  Draw and label a longitudinal wave.

 Name 4 properties of waves.  Which property of a wave is the distance from crest to crest?  Which property of a wave is the distance the medium moves from its resting position?  How much faster do light waves travel than sound waves?  What is the formula for calculating the speed of a wave?  Which type of wave moves the medium in a direction PARALLEL to the direction of the wave?

Exit Slip 1. What is a mechanical wave? 2. What are the two types of mechanical waves? 3. Illustrate a crest & trough and explain them in your own words. 4. Make a Venn Diagram to compare and contrast transverse and longitudinal waves.

Update your Do-Now Chart Today ’ s Goals PredictionActual Identify & describe 4 properties of waves Use the formula v=λf 1.Amplitude 2.Wavelength 3.Frequency 4.Speed v = velocity (speed) λ = wavelength f = frequency v= λf f=v/ λ λ=v/f