Is there an appreciable Doppler effect when the motion of the source is right angles to a listener?

Question

please explain! Thanks in advance!

Answer 1

A meteriologist/ weather caster would know better. Also try contacting your local National weather Agency to ask. I know that Fox.com (Foxs News) has a great Doppler Radar, the angles you can view them in are also great.  

Answer 2

yes. if something is going at right angles, it is still getting closer/farther away, so the same principle applies.

if you mean it is circling the observer....then i think the frequency would stay constant.  

Answer 3

If the distance is increasing or decreasing, YES.

Draw a right triangle and try adjusting the lags on the right angle. You will see the others get farther or closer.  

Answer 4

No. There is no Doppler effect in perpendicular direction.

That is there is SR perpendicular Doppler effect, but it's another story.

Answer 5

trrt

Answer 6

I dont understand what you mean by right angles to the listener.

Answer 7

If it the motion is initially at a right angle to the observer, and continues in a straight line, then yes there is a Doppler effect because the object is moving away from the observer.

But be clear on a few things:

1) If it continues in a straight line, the angle is no longer 90 degrees but is instead constantly changing.

2) When moving at a right angle to the observer, it's impossible for it to be approaching the observer, it must be moving away, so the doppler effect will always be a redshift.

3) If, instead of continuing in a straight line, it circles the observer, the angle will stay at a constant 90 degrees and there will be NO doppler effect.

Answer 8

I assume you mean, "is at a right angle to the motion of the listener".

The answer is yes.

The Doppler effect is present at any time when the source and listener are moving relative to one another.

Answer 9

If this isn't what you mean, let me know, but I tried to draw a crude ascii diagram to make it more clear. So you have a source separated by some distance d from the listener. The source is moving perpendicular to a line connecting the listener and the source?

..........................^

..........................I  

Listener ----------Source

Ignore the dots, sorry, Yahoo won't let me format this like I want to.

If so, then no, at least as long as the source continues moving perpendicular to the radius connecting the listener and the source (i.e. in a circle around the listener). This is kind of awkward to talk about just in words.

So sound is made up of waves, right? And the pitch of a sound is determined by the frequency of those waves, or by how rapidly a listener observes the wave going through a full cycle of crest to trough and back again. Let's say the the source emits a full wavelength once every second -- that is, 1 second elapses between each crest of the wave it emits. Then if the listener is stationary with respect to the source, it detects a crest in the wave coming in, then 1 second later, it sees another crest, so it hears the same frequency that the source does -- one wavelength per second. Now imagine that the listener is moving toward the source. It detects a crest at Point A. Then 1 second later, another crest strikes Point A. However, by now, the listener is at Point B, which is closer to the source, so it's seen more than a full wavelength in 1 second. It thus concludes that the frequency is higher than one wavelength per second, so it hears a different pitch. This is what causes the Doppler effect.

Now let's look at your case. The distance between the two objects is always the same, so no Doppler effect arises. If the source emits a crest, the next crest will always strike the listener 1 second later, although it might come from a slightly different direction. Thus, no Doppler effect occurs. There may be more complicated effects that would come about in practice from weird stuff with air currents, but I don't know about this.

If the source ever stops traveling at right angles with respect to the listener, and is allowed to move in a straight line, the Doppler effect should be easily calculated with standard formulas, but plugging in the instantaneous rate of change of the distance between the objects for velocity. This could produce a significant effect.