6 Determine the Speed of Sound in Air

Question 1

how can the frequency of a signal be measured from a oscilloscope

Answer 1

the time between two identical points on adjacent waves can be measured from the time axis. this is the time period of the signal. the frequency is given by the inverse of the time period

Question 2

what two traces should be displayed on the oscilloscope screen

Answer 2

the signal sent by the loud speaker and the signal received by the microphone should both be displayed

Question 3

describe what happens to the two traces as distance between the speaker and the microphone is increased

Answer 3

the two traces will move past each other and the phase difference between them will change

Question 4

what piece of apparatus should be connected to the loud speaker to produce a tone

Answer 4

a signal generator which should also be connected to the oscilloscope

Question 5

how should the speaker and the microscope be positioned on the oscilloscope

Answer 5

the spacing of the signals inputted into the oscilloscope should eb changed so that one is above the other. peak of the lower trace should align with the trough of the upper trace

Question 6

how should the initial separation of the speaker and microphone be set

Answer 6

so that the traces align as previously described and the distance should then be measured

Question 7

how can the wavelength be determined by moving the speaker away from the microphone

Answer 7

should be moved until the peak and trough of the traces align again. the distance moved will then be the wavelength

Question 8

what uncertainties are involved in this experiment

Answer 8

when determining the frequency there is an uncertainty due to the resolution of the oscilloscope. the traces also have a thickness which will make their alignment harder to judge

Question 9

how should the scales on the oscilloscope be set

Answer 9

so that each trace displays about three wave cycles on screen

Question 10

how should the frequency values in this experiment be chosen

Answer 10

so that the wavelength is easily measurable. 4kHz is suitable

Question 11

why does the trace moving past each other by a complete wave cycle signify that the speaker has moved a wavelength

Answer 11

one cycle is the time period. the distance the wave travels in this time is one wavelength

Question 12

why is it advantageous to measure the frequency from the oscilloscope rather than the given one on the generator

Answer 12

a greater resolution will be obtained measuring from the oscilloscope