Diffraction Grating: Laser Illumination & 643 nm Wavelength

[cyclonefb3]

Homework Statement

A laser is used to illuminate a diffraction grating that has spacing of 637 lines per mm. The grating sits 11.6 cm in front of a screen. Find the distance to the first and second maxima (y1 and y2) for the laser wavelength of 643 nm. Express your answers in mm.

Homework Equations

wavelength = (s/m)(y_m/sqrt(L²+y_m²))

The Attempt at a Solution

s = 1/637 = .00156 mm
L = 116 mm
wavelength = 643 X 10^-6 mm

I tried solving this equation for y_m, but the answer I got was wrong. Is there another way to do this problem?

 

[alphysicist]

Hi cyclonefb3,

What answers did you get?

 

[cyclonefb3]

I got 116 mm for both.

 

[alphysicist]

I got 116 mm for both.

Can you show the details of how you got those two answers (what numbers you used and so forth)? I'm not getting that from your equation.