Doppler1



		An Example about the Doppler Effect:

A DJ is playing some nice music using the usual frequency of your favorite radio station (9.7 MegaHertz) but he is travelling (with all the equipment to transmit radio waves) on a space ship. The velocity of the spaceship is that of a typical star moving around the galaxy (for example the Sun is mobing at 250 km/s ). At which frequency you will have to move the dial if the spaceship is moving towards at that velocity? What about if it is moving away?

	When moving source is approaching the frequency observed is given by the formula f_observed= v / (v+v_source) f_source where v is the velocity of the wave (c in the case of light) Substituting the numbers in the example we have: f_observed= 3x10⁸ m/s / (3x10⁸ m/s +2.5x10⁵m/s) 9.7x10⁶Hertz =9.69 1x 10⁶ Hertz You can see, that even at this very high speed the change in frequency is very small. But it is observable, and we can use it to determine the velocity of fast moving objects. When the source is going away the frequency observed is given by the formula f_observed= v / (v-v_source) f_source f_observed= 3x10⁸ m/s / (3x10⁸ m/s -2.5x10⁵m/s) 9.7x10⁶Hertz =9.708x 10⁶ Hertz

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