I figured half the problem, but I am not sure where to go from there... The hydr

Question

I figured half the problem, but I am not sure where to go from there...

The hydrogen spectrum has a red line at 656nm and violet at 434nm. What angular seperation between these 2 spectral lines is obtained with a diffraction grating of 4500lines/cm.

Red angle 17.12 Violet angle 11.26

My prof gives a handout with the steps and the next steps he used were tan0= y/L for each color and then find the change in Y to solve for L. I don't understand how to get the delta Y without L.

Thanks is advance!!

Vanessa

Explanation / Answer

the wavelength of red line is lamda1 = 656 nm = 656 x 10^-9 m

the wavelength of violet line is lamda2 = 434 nm = 434 x 10^-9 m

let n be the number of lines per cm on the diffraction grating

we know that

n = lamda1 x theta1

or theta1 = (n/lamda1)

similarly,

theta2 = (n/lamda2)

the angular separation is

d(theta) = theta2 - theta1

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