AH Exp – Wave Phenomena 02 – Determination of the thickness of a sheet of paper using wedge fringes

Aim – To determine the thickness of a sheep of paper using the interference fringes produced by a thin wedge.

Instructions

The sodium lamp produces monochromatic light of frequency 5.89 x 10^-7 m.

▪ Switch on the sodium lamp.
▪ Position one of the fringes in the centre of the cross hairs in the eyepiece view of the travelling microscope.
▪ Measure the position of the travelling microscope using the Vernier scale.
▪ Move the travelling microscope and measure the separation of 20 fringes
▪ Calculate the thickness of the paper, using the equation Δx=λL/2D where D is the thickness of the paper, and Δx is the spacing of the fringes.

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