RC

# In physics, redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum. The phenomenon is commonly seen in the spectra of astronomical objects. It can be seen in the spectra of stars, quasars, and galaxies. The observed redshift is proportional to the object's distance from the observer, and was first noticed in the 18th century by astronomer William Herschel. The most commonly accepted explanation of the redshift is that it is a Doppler shift that is proportional to the object's relative velocity with respect to the observer.

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#### Physics 103

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welcome to our third example video. Looking at relativistic energy and the Doppler effect for light. In this video, we're going to consider rocket ship that is traveling away from the Earth and wants to receive signals from it. So in this case, we're generating some signal here Earth F not. But the rocket ship is going to receive some frequency F, given that it's moving away from us with a speed equal to 0.7 the speed of light. So they need to adjust for this shift so that they can actually get the correct frequencies when they arrive at us, when, when the when the signal arrives at them. In order to do that, we consider our Doppler shift. We have F is equal to f, not multiplied by one minus the oversee, divided by one plus B oversee and when we have this, weakens quickly solve for F, not as being equal to F multiplied by the square root of one plus fee oversee divided by one minus the oversee. So if we say that we sent out if we receive a frequency of 1000 hertz, we can interpret what Earth is sending us by using this equation that is 1000 hertz is equal to F or rather, if not is equal to 1000 hertz multiplied by the square root of one plus 10.7, divided by one minus 10.7. And what we get for this is that they're sending a frequency of 2380 hertz. So we are receiving a significantly smaller frequency than what was actually sent to us. But knowing that this shift is occurring, we can account for it now. On the other hand, I should mention if we were traveling towards the Earth that the equation we've developed here is actually favorable for objects moved for objects that are moving away from a source. If we're moving directly towards the source, then we would need to use instead so for towards the source we would need to use F is equal to f not multiplied by. We simply change the science one plus v oversee divided by one minus B oversee, and we'll find here that we get the same a similar effect where, as we're moving away, we expect to receive a lower frequency. When we're moving towards it. We would expect to receive ah higher frequency than what's being sent

RC
University of North Carolina at Chapel Hill

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Quantum Physics

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Condensed Matter Physics

##### Top Physics 103 Educators  ##### Christina K.

Rutgers, The State University of New Jersey ##### Aspen F.

University of Sheffield 