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penguinboat
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Question one:
A drill sergeant standing just inside a bunker doorway that is 0.951 m wide blows a whistle to summon the cadets from the exercise yard. Everyone responds except for Eli, who was about 90 m away from the bunker, at an angle of 18.3 degrees from a line normal to the doorway. Eli claims that he did not hear the whistle because he was standing at the second-order diffraction minimum for the sound waves. What whistle frequency is consistent with his explanation? The speed of sound is 343 m/s at this temperature.
Question two:
The Mystic Bright Fringes, the hippie disco band, is holding its thirty-year reunion concert at the Hollywood Bowl. The show opens with the stage dark except for a giant rotating mirrored disco ball, 2.35 m in diameter, illuminated by a laser beam shining through a pinhole aperture from the far back of the open amphitheater, 325 m away. The laser uses light of wavelength 671 nm and has an adjustable aperture. What should the diameter of the laser aperture be so that the central bright spot of the laser's diffraction pattern just covers the disco ball?
A drill sergeant standing just inside a bunker doorway that is 0.951 m wide blows a whistle to summon the cadets from the exercise yard. Everyone responds except for Eli, who was about 90 m away from the bunker, at an angle of 18.3 degrees from a line normal to the doorway. Eli claims that he did not hear the whistle because he was standing at the second-order diffraction minimum for the sound waves. What whistle frequency is consistent with his explanation? The speed of sound is 343 m/s at this temperature.
Question two:
The Mystic Bright Fringes, the hippie disco band, is holding its thirty-year reunion concert at the Hollywood Bowl. The show opens with the stage dark except for a giant rotating mirrored disco ball, 2.35 m in diameter, illuminated by a laser beam shining through a pinhole aperture from the far back of the open amphitheater, 325 m away. The laser uses light of wavelength 671 nm and has an adjustable aperture. What should the diameter of the laser aperture be so that the central bright spot of the laser's diffraction pattern just covers the disco ball?