Apparatus :
A. LASER source
B. Grating
C. Ruler
D. Screen

Procedure in laboratory (diagram) :

A. Measuring the distance between :

1. screen and grating (L)
   
2. 0^th order and 1st order interference (S₁) and 0th order and 2nd order interference (S₂)
   
   

B. Determine the wavelength of the LASER using diffraction equation :
1. determination of the angle

2. determination of the wavelength

Procedure in laboratory :

Data and the analysis :

Given, the grating has 13600 lines per inch (grating constant).
That means distance between two consecutive lines (d) = (1 ÷ 13600) = 7.35×10^-5 inch

note that, 1 inch= 2.54 cm
∴ spacing of the grating (d) = 7.353482 × 10^-5 × 2.54 cm = 1.867784 × 10^-4cm

Analysis :
A. Determine the distance between the grating and the screen.
B. Note down the distance between the zeroth order interference pattern with the First and second order interference pattern.
C. Calculate the value of wavelength of the LASER using diffraction law.