Precision Inferometer

Using a prism spectrometer, it is possible to measure the wavelength (λ=589.3 nm) of the characteristic yellow emission lines of a sodium lamp. However, the spectral resolution of the prism is insufficient to separate the two component emission lines, denoted D1 and D2. A precision interferometer can be used to achieve this.   

In this experiment, you will measure the wavelength difference, λ₂-λ_1, between the sodium D lines using the interferometer in its Fabry-Perot mode of operation.

For context, the Michelson interferometer is probably best known because of its use in the Michelson-Morley experiment, which was designed to demonstrate the motion of the Earth through the ‘aether’. In fact, no such motion was detected, and this led to the abandonment of the concept of the aether. This resulted in Einstein adopting the theory of special relativity and the postulate that the velocity of light is independent of the motion of its source. 

There is an ISE where you can practice this experiment before your session that can be found here. Current students can find more information on Learn Ultra.