Diffraction and interference


by Nemanja989
Tags: diffraction, interference
Nemanja989
Nemanja989 is offline
#1
Mar24-11, 03:04 PM
P: 49
Hello,

could someone tell me what is the main difference between effects of diffraction and interference?

For now, I think that diffraction is name for deviation of waves when they come to obstacle.
And interference is phenomenon when two or more waves are in superposition in some point in space.

But the main thing that I do not understand is the difference between diffraction and interference picture. I simply think that those two are the same, because, first wave has to do diffraction on some obstacle and after that to interferes with itself.

Thanks!!!
Phys.Org News Partner Physics news on Phys.org
The hemihelix: Scientists discover a new shape using rubber bands (w/ video)
Mapping the road to quantum gravity
Chameleon crystals could enable active camouflage (w/ video)
RedX
RedX is offline
#2
Mar24-11, 06:13 PM
P: 969
Quote Quote by Nemanja989 View Post
Hello,

could someone tell me what is the main difference between effects of diffraction and interference?

For now, I think that diffraction is name for deviation of waves when they come to obstacle.
And interference is phenomenon when two or more waves are in superposition in some point in space.

But the main thing that I do not understand is the difference between diffraction and interference picture. I simply think that those two are the same, because, first wave has to do diffraction on some obstacle and after that to interferes with itself.

Thanks!!!
I think diffraction is the term used when interference is caused by multiple sources that are being driven by a single source.
Drakkith
Drakkith is offline
#3
Mar24-11, 08:16 PM
PF Gold
Drakkith's Avatar
P: 11,057
Quote Quote by Nemanja989 View Post
Hello,

could someone tell me what is the main difference between effects of diffraction and interference?

For now, I think that diffraction is name for deviation of waves when they come to obstacle.
And interference is phenomenon when two or more waves are in superposition in some point in space.

But the main thing that I do not understand is the difference between diffraction and interference picture. I simply think that those two are the same, because, first wave has to do diffraction on some obstacle and after that to interferes with itself.

Thanks!!!
A wave can diffract without interfering with itself. They are seperate phenomena that you have already defined in your post.

netheril96
netheril96 is offline
#4
Mar24-11, 09:12 PM
P: 193

Diffraction and interference


Diffraction and interference are basically the same, but the former is interference of (uncountably) infinitely many waves and the latter finite.
Nemanja989
Nemanja989 is offline
#5
Mar25-11, 12:58 AM
P: 49
Well, ok if diffraction is term for deviation of waves when they come to the obstacle, then there can not be such thing as diffraction picture, right? It is interference picture, because there is superposition of waves in some point in space, but before that diffraction happened.

I understand all of physics of waves, but I do not know why do they have term "diffraction picture" when it obviously comes from interference in last step (but still can't happen without diffraction).

From physical point of view they could call Fraunhofer diffraction, something like Fraunhofer interference? And same with Fresnel.

In fact, I would like to ask what is the difference between diffraction picture and interference picture?
jtbell
jtbell is offline
#6
Mar25-11, 08:06 AM
Mentor
jtbell's Avatar
P: 11,255
The phenomena that we commonly label as "interference" (e.g. of light passing through two slits) and "diffraction" (e.g. of light passing through one slit) are both the result of superposition / interference of waves.

We commonly use "interference" to refer to superposition of waves from a discrete number of sources, e.g. two narrow slits, three narrow slits, or a diffraction grating. We commonly use "diffraction" to refer to superposition of waves from a continuous set of sources, e.g. the continuous range of points across the width of a wide slit.

Two narrow slits gives you a pure interference pattern. A single wide slit gives you a pure diffraction pattern. Two wide slits gives you a combination of diffraction and interference.

Double slit interference

Single slit diffraction

Double slit diffraction (The "single slit envelope" is the "diffraction" part of the pattern, and the narrower peaks are the "interference" part.)
Nemanja989
Nemanja989 is offline
#7
Mar25-11, 10:07 AM
P: 49
@ jtbell

Thank you very much, I finally understood the main difference between interference and diffraction phenomena :) .


Register to reply

Related Discussions
diffraction vs interference General Physics 2
Diffraction and Interference Introductory Physics Homework 3
Interference and Diffraction Introductory Physics Homework 0
Interference and Diffraction Introductory Physics Homework 7
Interference, Diffraction, Diffraction Grading General Physics 1