If two waves are shifted by ________, completely destructive interference
will occur.
☑ l/2
☐ 2l/3
☐ l
☐ 2l
In a standing wave, the points that have the maximum vibration are
called:
☐ nodes
☑ anti-nodes
You have two pipes which produce sound: one is open at both ends
(like an organ pipe) and the
other is open at only one end (like a panpipe). If the two pipes have the same length, the
fundamental resonant frequency will be ____________ for the two.
☐ the same
☑ different
Ralph recently saw this bumper-sticker on a professor's car:
"If this sticker is blue,
you're driving too fast!" (True story: a professor at my previous
university had the sticker on her car.) The sticker looks RED to him. He is confused. Can
you explain the joke to Ralph? (Note: Light undergoes a Doppler effect similar
to sound, although the precise equation is slightly different than the one for
sound given in the textbook. Also, you need to know that red light and blue
light both travel at c = 3´108 m/s, but red light has a longer wavelength than blue.)
Due to the Doppler effect, frequency shifts up when an observer (the car in back of you) moves towards a source (your bumper sticker). The joke here, is that with light you would only get a shift significant enough to change red to blue when the observer is moving at a substantial fraction of the speed of light.