The Doppler Effect - Sound source approaching

Question	Answer
What happens when the sound source is approaching the observer?	The wavelength between the sound waves closest to the observer become smaller
What happens to the frequency? Use the formula c=fλ	From this, we see that the frequency is inversely proportional to the wavelength: f=\[\frac{c}{λ}\]
So, when the wavelength becomes smaller, the frequency becomes bigger	Thus, the noise from the sound source appears louder
We can use this theory and a formula to calculate the apparent frequency of the source	It's important to note that the frequency itself doesn't change, it's an apparent change
We use the formula f'=\(\frac{v}{v±vs}\)f	f' = Apparent frequency v= Speed of wave vs = Velocity of the source f = frequency of the source
When the source is moving away, we use a minus on the bottom of the fraction:	f'=\(\frac{v}{v-vs}\)f
Just remember that the apparent frequency is going to be greater,	So the bigger the smaller fraction is, the bigger f' will be, so use the minus!
And check your answers, if you know the object is approaching but you get a smaller apparent frequency...	You've gone wrong somewhere!!!

Resource summary

	Created by leonie.examtime over 10 years ago

	Copied by ed.wilson89 over 10 years ago