00:01
Okay, in this question here, we have monochromatic light, which is instant on a plane transmission grating.
00:05
We're told that the first order maximum in the interference pattern is an angle of 8 .33 degrees.
00:11
We'll write that in there, 8 .33 degrees.
00:14
And we'll ask, what's the angle position of the fourth order maximum? so what's this angle going to be here? so in order to do this, we're going to need to state the equation relating to diffraction grating.
00:24
So n lambda is equal to d sine theta, where n is the order number.
00:30
Lambda is the way of the light being used.
00:33
D is the grating spacing, and then we have sign and then the angle relating to the order number.
00:41
So sign theta n.
00:43
And you might say here, well, hang on, how can we do this? we want to find theta, and we know that n is equal to four, but we don't have lambda or d.
00:54
We have two unknowns, therefore surely it's not possible.
00:56
And well, if we actually rearrange to say lambda over d equals sine theta over n, i'll say sine theta n over n.
01:09
Then we can see that lambda over d must be a constant because the wavelength is going to say the same...