For optical filtering and generation of interference rings in the experiment to demonstrate the normal Zeeman effect. The fixed etalon consists of a substrate with highly reflective, if only partially reflecting, mirror coatings on both sides. The substrate and mirrors form an optical resonator which fulfils the resonance conditions for a specific wavelength of 643.8 nm, which is that of the red cadmium line.
The inclination of the etalon to the optical axis can be adjusted by means of adjustment screws in the frame, allowing the pattern of the interference rings to be shifted both horizontally and vertically.
Wavelength: 644 nm
Substrate material: Suprasil
Refractive index: 1,4567
Coefficient of reflection: 0,85
Flatness: 32 nm (λ/20)
Aperture: 22 mm
External diameter: 130 mm
Diameter of rod: 10 mm
Height from end of rod to optical axis: 150 mm