Name of Experiment: Laser Diffraction
Exp. No. (1):
Aim of Exp: To Determine the wavelength of the Helium – Neon Laser.
Apparatus:
1.
2.
3.
4.
5.
Laser source.
Holders.
Screen.
Grating or small hole.
Scale (100) cm.
Method:
A- By using small hole:
 Adjust the Laser rays toward the small hole in order to include the
diffraction pattern (bright and dark circle).
 Measure the distance between the hole and screen and measure (2l).
 By using Brig law:
m λ= d sin Ɵ
Calculate the wavelength of Laser light.
Where m = No. of rank,
λ = Wavelength Laser light,
d = Diameter of hole, and Ɵ is very small then sin Ɵ = tan Ɵ = Ɵ
A- By using grating:
m
2l
l
tan Ɵ = l / L
1.
2.
3.
 Plot a graph between (m) and tan Ɵ.
 Calculate:
 slope = m / tan Ɵ
 d = slope * λ
 d = 1/ N
where N: No. of grating.
Discussion:
1. Define Laser and compare it with other light.
2. Explain types of Laser. Give example for each one and refer to the
wavelengths, power, and fluence of it.
3. Discuss medical application for Different types of Laser.