The experimental setup to measure the wavelength of Lasers will be described. Many of the Lab Equipment needed can be obtained from Home Science Tools as well as other sources.
In order to make a double slit for the experiment, it is a good idea to purchase the Optical Slit Kit from Home Science Tools. For our purposes it has a Graphite Alcohol Solution that can be used to coat a microscope slide in a black coating to block light. It also has razors that can be used to create the double slit. Two razors are pressed together and used to draw out two closely spaced slits.
To mount the Laser and point to a square paper sheet with mm markings at a distance of L=880mm use a Ring Stand and the Prong Universal Clamp from Home Science Tools.
We can also conveniently use the Burette Clamp for the Ring Stand to hold the slide with the double slit and also the Square Paper with mm markings.
The diagram below shows the double slit geometry. Since we are using lasers we don't need the single slit. The distance between the slits is "a". The distance to the Square Paper with mm markings is "L". From the interference pattern on the paper and the mm markings we can obtain the distance between peaks as "delta y". We can then proceed to calculate the wavelength. See description below.
Double Slit Diagram Reference: Pedrotti, Frank L.; Pedrotti, Leno M.; Pedrotti, Leno S.. Introduction to Optics (p. 170). Cambridge University Press. Kindle Edition.
In order to measure "a" we use an AmScope T490B-DK Compound Trinocular Microscope. The image below is obtained form the Microscope. We use an AmScope MR095 Microscope Stage Calibration Slide for USB Camera 0.01mm Stage Micrometer to obtain "a". See the photos below. We also used Photoshop to obtain the composite image with the Double Slit and the 0.01 mm calibration.
A Double Slit Under Microscope (Different Than the One Used See Below)
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Measurement of Double Slit Separation "a" 10 Microns Per Division
From the Microscope a=150 Microns.
Interference Pattern Per Laser and Measurement of Delta Y.
The key formula is:
We know "delta y", "L" and "a", so we can calculate the wavelength for each laser.
Check against the table below.
