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I know that Doppler effect occurs in sound because 1. sound is mechanical and requires a medium to propagate and 2. velocity of light is the same in all “inertial frames” where as sound is not but why is diffraction not as common in light as opposed to sound

2007-03-03 13:40:31 · 5 answers · asked by Anonymous in Science & Mathematics Physics

5 answers

Oh, but they are observed in light!!!!! That is how Hubble discovered that the universe is expanding. The velocity of light is not changing, and the velocity of sound is not changing in the Doppler effect. It is the wavelength of each that is effected. The waves are compressed as an object moves toward you so the wave lengths are shorter. As an object moves away from you the waves are elongated so the wave lengths get longer. That is the reason for the difference in sound and the different shifts noted in the electromagnetic spectrum. A "red shift" means the object emitting the light is moving away from you while a "blue shift" means the object is moving toward you. Hubble noticed a "red shift" in the electromagnetic spectrum of distant stars and realized that they were actually moving away from us - therefore the universe is expanding.

2007-03-03 13:43:50 · answer #1 · answered by physandchemteach 7 · 2 0

The Doppler Effect and diffraction are just as common in light waves. Light only does this more subtly.
The only reason this is harder to observe with light is because it moves so fast, that motion does not make a discernible difference until it reaches very high velocities.

2007-03-03 13:45:55 · answer #2 · answered by Renaissance Man 1 · 1 0

Doppler effect is observed with light too (Einstein's Relativity is about that). Since sound travels with a lot slover speed than light it is possible for us to observe the Doppler effect in sound. Speed of light is constant only in vacuum. In a medium with heavy refractive index light diffracts too.

2007-03-03 14:20:17 · answer #3 · answered by MERAJ S 1 · 0 0

Both effects are observed with light, but harder to see for two reasons. The wavelength of light is much shorter than sound, so diffraction is harder to observe. The velocity of light is much higher than that of sound, so you need to move much faster to observe it. Two other differences are that light is a transverse wave (sideways) but sound is longitudinal (to-and-fro in the direction it is moving). Also the speed of sound in air is fixed relative to the air, so its speed relative to you depends on how fast you're moving, but light moves through empty space, so if you and I are moving at different speeds, we both measure its speed to be the same; 300 000 km a second.

2007-03-03 13:58:18 · answer #4 · answered by zee_prime 6 · 0 0

light waves diffract. you can see this by closing the door of an illuminated room while you stay outside and it should be dark. you should see light peeking along the edges of the door. that's diffraction. or you can notice it with your shadow. it doesn't have that abrupt change in contrast because of diffraction.

with regards to doppler shift of light waves, we're unfortunately unable to detect this...

2007-03-03 14:08:04 · answer #5 · answered by riddler 1 · 0 0

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