Ad Hoc Experiment Showing Diffraction of Red, Green and Blue
Lasers from a 1000 lines/mm Diffraction Grating
For the Diffraction Grating, 1000 lines/mm see Home Science Tool. For holding the Laser use a Ring Stand and the Prong Universal Clamp from Home Science Tools.
The experiment is a great way to understand how a Diffraction Grating can be used in Spectroscopy.
Lasers Through Diffraction Grating
As the Wavelength increases so does the deflection.
To understand the theory behind the diffraction grating, see Chapter 10 in the reference below:
Electromagnetics and Optics E E Kriezis (Aristotle Univ. of Thessaloniki), D P Chrissoulidis (Aristotle Univ. of Thessaloniki), and A G Papagiannakis (Aristotle Univ. of Thessaloniki) Default Book Series.March 1992
The theory relates the number of lines/mm (related to 
in the Figure) to the amount of the deflection. The Harmonic Amplitude Variation model allows for a nice theoretical development. The deflection is inversely proportional to so that, as the number of lines/mm increases, the deflection is larger.
https://en.wikipedia.org/wiki/Visible_spectrum