Iona Prep Physics Puzzles

Lab: To Measure the speed of sound in an unknown gas

You already calculated the speed of sound in air using resonance in the laboratory. You did that by knowing the frequency of the sound, measuring its wavelength and then using the relationship

to calculate the speed.

This iLab is similar, but different in some ways:

• Sound travels at different speeds in different gasses. You will not be using air in this experiment, but an unknown (to you) gas..
• There is an electronic signal generator (not a tuning fork) generating the sound.
• You choose the frequency which is generated by the electronic signal generator.
• The generator drives a speaker which is emitting sound into a glass tube.
• The tube is closed by a piston which can move. The wavelength is determined by moving the piston.
• The computer measures the wavelength of the sound by moving the piston.
• The computer returns a web page to you with frequency and wavelength information.
• You use the relationship above to calculate the speed of sound in that gas.

Experimental Setup:

Of course a single run will not give perfect results. You should run the experiment several times, put your data into a table, compute the speed for each run and then use the average speed as your conclusion:

Conclusion: the speed of sound in the unknown gas was found to be .........