Q1. A tuning fork is struck and the following waveform drawn out on an oscilloscope:



If each horizontal division on the scale of the oscilloscope represents 0.0005 seconds. What is the frequency of the tuning fork?


A1. The wave has a period of 7 segments of 0.0005 s each, or a period of 0.0035 s. The period of the tuning fork is therefore 0.0035s



Q2. There are two main types of internet "broadband" service, wired and wireless. The wireless or "WiFi" option uses electromagnetic radiation with a frequency of either 2400 MHz or 5000 MHz. Calculate the wavelength of the EM emissions in both cases, given the speed of the wave as 3 x 108 m/s.


A2. The equation we use will be the same in each case, note that we need to convert frequencies to Hz but we can remain in "standard form" to do this by multiplying 2400 and 5000 by 106. 



Q3. A musician plays a note of wavelength 25 cm on his synthesiser. He knows the speed of sound is 340 m/s in air. What is the note's frequency? 


A3. Remember to convert units where necessary. 25cm = 0.25m



Q4. A student drops a stone into a large pond, she then counts 5 waves on the pond in 10 s. The distance between them is 80 cm. What is their speed? 


A4. Again, watch the units, you are told that "the distance between the waves" (which is the wavelength) is 80cm=0.8m. 5 waves in 10s gives a frequency of half a wave per second, or 0.5 Hz.



Q5. On the back of a microwave oven is a label which reads "frequency = 2,450 MHz". The speed of microwaves is 3.00×108 m/s. What wavelength are they? 


A5. 2450Mhz is 2,450,000,000 or 2.45 x 109 Hz



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