To: the teacher Each student will need a formula foldable for velocity of a wavelength and a piece of paper for reflection, diffraction, refraction, resonance foldable

Waves Waves

IPC 5 B Demonstrate wave interactions including interference, polarization, reflection, refraction, and resonance with various materials.

What is a wave? Definition: a wiggle in space and time –Waves transfer energy Medium: substance that waves travel through. –Waves travel fastest in solids –Waves travel slowest in gas What causes waves? Vibration of molecules

Types of waves Transverse waves – ocean waves, light waves, radio Parts: Crest – high point Trough – low point Longitudinal waves – sound waves Parts Compression – high pressure Rarefaction – low pressure

Rarefaction Compression Trough Crest Amplitude

Sound Wave (Compressional) A slinky is a good example of how compressional waves behave. Sound particles vibrate against one another causing compressions

Interference Constructive – builds the amplitude Destructive – decreases the amplitude

Basic wave properties All waves have 4 basic properties Amplitude – The height of a wave Wavelength – the distance between crests or compressions Length of one wave (“S” shape) Frequency – how often a wave occurs in a time frame (cycles/sec, wiggles/sec, ) Hertz Velocity – how fast a wave can occur in a time span

Amplitude Height (volume) of crest or trough from NODAL Line, measured in decibels (db) the total energy of the wave Height (volume) of crest or trough from NODAL Line, measured in decibels (db) the total energy of the wave Amplitude or

Wavelength Wavelength and frequency are inversely proportional to each other. Longer wavelength / Lower frequency Shorter wavelength / Higher frequency

Which label on the model to the right, represents a wavelength? A.) Q B.) R C.) S D.) T Practice Questions

Frequency The number of wave crests that pass one place each second. (Measured in Hertz) Ex. The frequency of vibrations gives the pitch on a guitar string Which wave has a higher frequency? A.A. A.A. B.B. B.B.

What would be the wavelength in centimeters of the wave, illustrated above, if its frequency were doubled? A.) 2.5 B.) 0.8 C.) D.) 0.4 Practice Questions

Formula Chart Constants, Symbols and Units Formulas Today we will work with the velocity of a wave formula. Find it on your Formula Chart.

Velocity of a Wave (Wave speed) Wavelength X Frequency V = ג x f Velocity = m/s Wavelength ( ג ) = meters Frequency = hertz (cycles/second)

TRIANGLE METHOD- V = f x ג V ג f X ÷ Velocity of a wave = frequency × wavelength

1. A wave has a wavelength of 15 cm and has a frequency of 10 waves/second. What is the speed of the wave? 2.The speed of a wave on a rope is 50cm/s and it’s wavelength is 10cm. What is it’s frequency? 3.A wave is traveling with a velocity of 125m/s and has a frequency of 20 waves/second. What is the length of the wave? Practice Questions

1. A wave has a wavelength of 15 cm and has a frequency of 10 waves/second. What is the speed of the wave? 150 cm/s 2.The speed of a wave on a rope is 50cm/s and it’s wavelength is 10cm. What is it’s frequency? 5 Hz 3.A wave is traveling with a velocity of 125m/s and has a frequency of 20 waves/second. What is the length of the wave? 6.25 m Practice Questions

Practice Question Which wave has the greatest velocity? V = f x ג Velocity = m/s Wavelength ( ג ) = meters Frequency = hertz (cycles/second) 2m x 8Hz = 16 m/s

Foldable Fold one piece of paper lengthwise Make three slits on the top page as shown below. Label each flap: Reflection, Diffraction, Refraction, Resonance (Complete the following while viewing next few slides) Under the flap write/draw an example On the bottom, write the definition Reflection Diffraction Refraction Resonance

Reflection Bouncing back of a wave as it strikes a hard surface. Example: When a wave from the ocean hits the beach Sound waves off a canyon wall Example: When a wave from the ocean hits the beach Sound waves off a canyon wall

Practice Questions When a DVD is read, laser light touches the DVD surface and is then measured at location A. What allows light to return to location A after striking the DVD surface? F Conduction G Refraction H Magnification J Reflection

Practice Questions An individual stands in the bottom of a canyon and yells. The sound echos back to the person. This is an example of: F Reflection G Refraction H Diffraction J Resonance

Diffraction When waves spread out past the edge of a barrier. Example: You can hear someone talking behind a corner, because the waves move beyond the wall. This is going to be a great surprise! Not anymore!

Practice Questions The diagram shows waves approaching a barrier. Which pattern will form after the waves pass through the opening in the barrier?

Practice Questions Light shines through a keyhole on a door. John notices that the shadow shape on the wall is much larger and fuzzier than the real keyhole outline. This is due to – A.refraction B.diffraction C.resonance D.reflection

Refraction To change the direction of a wave as it passes from one medium to another. (the “bending” of waves)

Practice Questions In the drawing to the right, the straw is actually in one piece, but appears to be in two pieces. How would you explain this phenomenon to your friends? A.) The liquid absorbs the light and reflects only certain colors B.) The liquid polarizes the light rays and causes some of them to be blocked C.) The liquid reflects the image from inside the glass D.) The liquid refracts the light rays by changing their speed and angle

Practice Questions Diverging lenses are useful to people who suffer from nearsightedness because the lenses can cause images of distant objects to be focused on the retina. Lenses allow images to be focused on the retina because of — F diffusion G reflection H diffraction J refraction

Resonance Causing another object to vibrate without contact by matching the natural frequency An opera singer can shatter a glass if the singer’s voice matches the natural frequency of the glass

Practice Questions One tuning fork is struck and placed next to an identical fork. The two forks do not touch. The second tuning fork starts to vibrate because of – A.interference B.the Doppler effect C.resonance D.standing waves

Practice Questions A guitar player is seated next to a piano. The piano player strikes an E key on the piano. The guitarist reports that this causes the E string on his guitar to vibrate. What is the name of this phenomenon? A Polarization B Resonance C Reflection D Diffraction

Practice Questions An empty cup was tightly covered with plastic wrap, and a few grains of salt were sprinkled on top of the plastic. When a tuning fork was struck and placed slightly above the plastic wrap, the salt began to move. Which characteristic of waves does the movement of the salt best demonstrate? A Echo formation B Diffraction C Resonance D Specular reflection

On the back of your foldable, name and define the 4 basic properties of waves 1.Amplitude – The height of a wave 2.Wavelength – the distance between crests or compressions Length of one wave (“S” shape) 3.Frequency – how often a wave occurs in a time frame (cycles/sec, wiggles/sec, ) Hertz 4.Velocity – how fast a wave can occur in a time span (EXAMPLE: 150 cm/s) 1 s

Wavelength Foldable-Make One Velocity of Wavelength ( V = f x ג) FORMULA UNITS SAMPLE PROBLEMS & SOLUTIONS

Types of Waves Seismic Ultrasound Light Sonar Echolocation Sound