Waves and Sound Honors Physics
Simple Harmonic Motion Refers to repetitive, cyclical motion (like a pendulum or waves) Can be described with sine curve For a pendulum only T 2 L g
Example problem The world s longest Foucault pendulum is in Seattle and it is 21.3 meters long. What is the period of this pendulum? What is the frequency of this pendulum?
Period and Frequency Period (T) 1 the time for one full cycle T measured in seconds f Frequency (f) the number of cycles in one second measured in Hertz (Hz) f 1 T
Example problem A pendulum swings back and forth 12 times in 4.0 seconds. What is the period of the pendulum? What is the frequency of the pendulum?
Waves A wave is a disturbance or oscillation back and forth that transfers energy (but not particles) through space.
Mechanical vs. Electromagnetic Mechanical Waves waves that travel through (and require) a physical medium (like water and slinky and sound waves) Electromagnetic Waves electric and magnetic disturbances that do NOT require a medium (like light and radio waves)
Waves Mechanical waves Wave that requires a physical medium to travel Electromagnetic waves Electromagnetic field disturbances that do NOT require a medium to travel Ex. Slinky, water, sound Ex. Light, radio wave, microwave Transverse Longitudinal Transverse
Transverse waves Disturbance is perpendicular to the direction of travel (propagation) Disturbance is up and down and travels left and right
Longitudinal waves (compression waves) Disturbance is parallel to the direction of travel (propagation) Disturbance is right or left and waves travel right or left
Parts of a wave
Wave Velocity The speed of the wave is determined by the medium only v = d t Frequency and amplitude do not change the speed of a wave v = f Frequency ( f ) and wavelength ( ) are inversely related
Example In the water, you see 7 waves go by in 12 seconds. The distance between crests is 2.5 m. The distance from flat water up to a crest is 1.5 m. Period =? Frequency =? Speed of wave =?
Example A transverse wave passes through a uniform material medium from left to right, as shown in the diagram below Which diagram best represents the direction of vibration of the particle, P, of the medium?
What is the wavelength of the transverse wave pictured here? a) 0.20 m b) 0.40 m c) 1.0 m d) 2.0 m e) 4.0 m
How many wavelengths are pictured in the diagram? a) 1.0 b) 2.0 c) 2.5 d) 3.0 e) 5.0
What is the amplitude of the wave pictured in the diagram? a) 0.20 m b) 0.40 m c) 1.0 m d) 2.0 m e) 4.0 m
Which points mark the crests of the wave?
List the letter(s) that are in phase with point C?
Interference (Principle of Superposition) When waves meet at a point in space, the resulting waveform is the addition of the amplitudes Constructive interference amplitudes add together to make bigger wave Destructive interference amplitudes subtract and form smaller wave or cancel for a moment Important: waves pass through each other after they interfere (waves are energy)
Example Two pulses traveling in the same uniform medium approach each other, as shown in the diagram below. Which diagram best represents the superposition of the two pulses?
Example Two pulses traveling in the same uniform medium approach each other, as shown in the diagram below. Which diagram best represents the superposition of the two pulses?
Example Two pulses traveling in the same uniform medium approach each other, as shown in the diagram below. Describe what happens after the two waves meet in space. The two waves will destructively interfere when they meet, but then the two waves will pass through each other and return to their same size and continue moving in the same direction.
Example The diagram below shows two pulses traveling toward each other in a uniform medium. Which diagram best represents the medium when the pulses meet at point X?