Diffraction Gratings, confusing question.

[skg94]

Homework Statement

Homework Equations

λ=xd/nl

The Attempt at a Solution

Im having some difficulty with the variables, is d= lines/m? and n= 27? from the 50 mark to the yellow mark. then x would be 27*(4.35*10^-6) and l would be 100cm=1m ?

 

[mfb]

d is the distance between lines at the grating.
n is the order of the line. As you have just one line for each color (0 would correspond to light directed towards the tube), it is 1.

then x would be 27*(4.35*10^-6)

That looks like xd, but it has no units and where does the value of 27 come from?

and l would be 100cm=1m ?

Right

 

[skg94]

27 lines from thr 50 to yellow

 

[mfb]

Those are lines on the ruler, they are completely arbitrary (you could use a ruler with mm-marks as well). 13.5cm is the physical quantity, it does not depend on the type of ruler.

 

[skg94]

i just assumed that because of the each etched mark is 4.35*10^-6 apart, so d would be 4.35*10^-6 but x would be that times the 27 lines from the distance from central to the node.

So x =.135m d= 4.35*10^-6 l =1 and n= 1 so really the calculation is (.135*4.35*10^-6) ?

 

[mfb]

With units, yes.

Those lines ~4µm apart are at the diffraction grating, not at the ruler.