A string vibrates at its third-harmonic frequency. The amplitude at a point 30 cm from one end is half the maximum amplitude. How long is the string?
The length of the string is 5.40 m
Third-harmonic frequency, n= 3The amplitude of the wave at x=30cm is Amax/2
The general expression of the amplitude of the wave at any distance x
According to the question Since it is three harmonic vibrations, there would be three loops with the length λ/2. Therefore, the total length of the string is given by Thus the length of the string is 5.40 m
Western music uses a musical scale with equal temperament tuning, which means that any two adjacent notes have the same frequency ratio r. That is, notes n and n + 1 are related by fn+1 = r fn for all n. In this system, the frequency doubles every 12notes—an interval called an octave.
a. What is the value of r?
b. Orchestras tune to the note A, which has a frequency of440 Hz. What is the frequency of the next note of the scale (called A-sharp)?
Engineers are testing a new thin-film coating whose index of refraction is less than that of glass. They deposit a 560-nm-thick layer on glass, then shine lasers on it. A red laser with a wavelength of 640 nm has no reflection at all, but a violet laser with a wavelength of 400 nm has a maximum reflection. How the coating behaves at other wavelengths is unknown. What is the coating’s index of refraction?
In 1866, the German scientist Adolph Kundt developed a
technique for accurately measuring the speed of sound in various gases. A long glass tube, known today as a Kundt’s tube, has a vibrating piston at one end and is closed at the other. Very finely ground particles of cork are sprinkled in the bottom of the tube before the piston is inserted. As the vibrating piston is slowly moved forward, there are a few positions that cause the cork particles to collect in small, regularly spaced piles along the bottom. FIGURE P17.53 shows an experiment in which the tube is filled with pure oxygen and the piston is driven at 400 Hz. What is the speed of sound in oxygen?
As the captain of the scientific team sent to Planet Physics, one
of your tasks is to measure g. You have a long, thin wire labeled
1.00 g/m and a 1.25 kg weight. You have your accurate space cadet
chronometer but, unfortunately, you seem to have forgotten a
meter stick. Undeterred, you first find the midpoint of the wire by
folding it in half. You then attach one end of the wire to the wall
of your laboratory, stretch it horizontally to pass over a pulley at
the midpoint of the wire, then tie the 1.25 kg weight to the end
hanging over the pulley. By vibrating the wire, and measuring
time with your chronometer, you find that the wire’s second harmonic
frequency is 100 Hz. Next, with the 1.25 kg weight still
tied to one end of the wire, you attach the other end to the ceiling
to make a pendulum. You find that the pendulum requires 314 s to
complete 100 oscillations. Pulling out your trusty calculator, you
get to work. What value of g will you report back to headquarters?
A trumpet player hears 5 beats per second when she plays a note and simultaneously sounds a 440 Hz tuning fork. After pulling her tuning valve out to slightly increase the length of her trumpet, she hears 3 beats per second against the tuning fork. Was her initial frequency 435 Hz or 445 Hz? Explain.
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