# Young's Light Interference

1. Sep 25, 2014

### JosefMTD

Hello!
I have done this experiment and managed to find this data:
http://puu.sh/bO8TJ/ac3520ec8b.png [Broken]

Am I right for saying that the position that reaches the value of 5 amps are the central bright and the position 220-ish as the 1st bright order and the position 260-ish as the 2nd bright order?

Or is it also okay to say that the position around 130 is a 1st bright order, the position around 90 is a 2nd bright order and position around 50 is a 3rd bright order and the position around 10 is the 4th bright order?

I'm having this doubt analyzing this data, can anyone help me clear my doubt?
Thank you.

Last edited by a moderator: May 7, 2017
2. Sep 26, 2014

### vanhees71

It would help a lot if you could describe your setup first. I guess it's a grating (multiple number of slits). So you have a grating-interference pattern with the interference pattern of the single slit as the envelop or something like this, I guess.

3. Sep 26, 2014

### Philip Wood

Strange envelope shape. Strange intensity units. Strangely even linear spacing of maxima, too, if this is a grating. Would be interesting to know the set-up.

4. Sep 26, 2014

### JosefMTD

Ya, this is a single slit enveloped a grating

5. Sep 26, 2014

### JosefMTD

Ya, this is a single slit enveloped a grating

6. Sep 27, 2014

### Philip Wood

I think this is hard to interpret. If the diffraction grating is a simple array of evenly spaced rectangular slits then the zeroth order beam would be the most intense, and the intensity of beams on either side would fall off, higher order beams becoming less intense. The reason for that is the 'modulating' single slit diffraction pattern, which gives the 'envelope'.

The pattern you have is not what I've just described, because the envelope is quite different in shape. This may be because you are using a diffraction grating which isn't much like an array of rectangular slits, but instead some other periodic variation of transmission as we go across the grating. It may be a reflection grating - you don't say which. The 'transmission profile' (or 'reflection profile') may be specially designed so the intensity is greater in certain higher orders.

Are we even dealing with light? Or some other electromagnetic wave?

With no more information than what you've given us, I'd say that your interpretation is quite likely to be the right one.

Last edited: Sep 27, 2014