Wave Properties

Answer Me!!! Can you break a wine glass using only your voice? Why?

Wave Fronts Imagine a pebble dropped into a lake. Waves don’t travel only in one direction from the pebble. Waves spread out in concentric circles from the pebble. Each solid circle represents the crest of a wave. All of the points on one crest are called a wave front.

Resonance Objects vibrate at a specific frequency when the object is hit, touched, etc. If two objects have the same natural frequency (resonance frequency), one will begin to vibrate if the other is struck. Opera singer breaking glass Tacoma Narrows Bridge Tuning forks

Practice Problem A tuning fork oscillates with a frequency of 256 Hz after being struck by a rubber mallet. Which phrase best describes the sound waves produced by this oscillating tuning fork? Electromagnetic waves that require no medium Electromagnetic waves that require a medium Mechanical waves that require no medium Mechanical waves that require a medium

Practice Problem 4 A nearby object may vibrate strongly when a specific frequency is emitted from a loudspeaker. What is this phenomena?

Diffraction Diffraction is the spreading of a wave into a region behind a barrier. A small opening in the barrier will produce a pronounced diffraction pattern If the opening in the barrier is larger than the incoming wavelength, there will be no diffraction.

Answer Me!!! As motorcycle drives by you, what sound does it make? Why?

Doppler Effect As the source of a constant frequency wave moves towards an observer, the wave’s observed frequency will be higher than the wave’s actual frequency. As the source of a constant frequency wave moves away from an observer, the wave’s observed frequency will be lower than the wave’s actual frequency. The higher the relative velocity, the more the observed frequency will change.

Doppler Effect - Sound Frequency of sound is observed as pitch. Higher frequency = Higher pitch Lower frequency = Lower pitch

Doppler Effect - Light Frequency of light is observed as color. Higher Frequency = towards violet Lower Frequency = towards red

Practice Problem 4 How can a radar gun effectively use the Doppler effect to measure velocity of oncoming vehicles?

Practice Problem 1 A 2.00 x 10 6 Hz radio signal is sent a distance of 7.30 x m from Earth to a spaceship orbiting Mars. The spaceship is moving away from Earth when the radio signal is received. Compared to the frequency of the signal sent from Earth, the frequency of the signal received will be

Practice Problem 3 A source of sound waves approaches a stationary observer through a uniform medium. Compared to the frequency and wavelength of the emitted sound, the observer would detect waves with a Higher frequency and shorter wavelength Higher frequency and longer wavelength Lower frequency and shorter wavelength Lower frequency and longer wavelength

Summarize On a separate sheet of paper, describe the Doppler effect and how it is observed in sound waves and light waves.

Answer Me!!!! If you see lightning strike and then 5 seconds later you hear the thunderclap from that strike, how far away from you did that lightning strike.

Superposition Superposition takes place when two or more waves travel through the same medium at the same time.

Constructive Interference When two waves are both positively (or both negatively) displaced constructive interference takes place. Maximum constructive interference takes place when both waves are in phase

Destructive Interference When one wave is positively displaced and the second wave is negatively displaced, destructive interference takes place. Maximum destructive interference takes place when waves are 180 o out of phase

Pulses in the Same Medium When two pulses pass through the same medium at the same time, they will interfere with each other.

Standing Waves Standing waves are made when two waves of the same amplitude and frequency travel in opposite directions in the same medium. In a standing wave, antinodes and nodes are stationary.

Practice Problem 1 Two pulses approach each other in a uniform medium. Draw the superposition of the two pulses.

Answer Me!!! Slowly walk through the aisles of the classroom. Then write down what you observe.

Two Source Interference The figure below shows the interference pattern coming from two point wave sources. Constructive interference takes place when the same kind of lines meet. Destructive interference takes place when dashed line meets solid line

Interference Pattern You can also determine whether destructive or constructive interference is taking place at a point by counting the number of wavelengths from each of the sources

Practice Problem 2 The diagram below represents water waves of length l from two point sources. What is the difference in length between the paths from each source to point P? P

Practice Problem 3 Two monochromatic, coherent light beams of the same wavelength converge on a screen. The point at which the beams converge appears dark. Which phenomena best explains this effect?