Calculate Fringe Separation in Fabry-Perot Etalon

[janrain]

problem:
in a spectrometer, one half of the slit is illuminated with mercury light and 2nd half illuminated with white light through a fabry-perot etalon. in the wavelength range of 4000 to 5000 angstorm , 20 fringes are observed in the continuous spectrum.
calculate the plate separation of the fabry perot etalon.

 

[Gokul43201]

https://www.physicsforums.com/showthread.php?t=4825

 

[janrain]

i don't know how to proceed. don't know the formula/what needs to be done to derive it.

 

[OlderDan]

i don't know how to proceed. don't know the formula/what needs to be done to derive it.

Read the section on the Fabry-Perot Etalon here

http://electron9.phys.utk.edu/optics421/modules/m5/Interferometers.htm

Save this link for a nice basic description of other interferometers.

The problem is telling you that there are 20 different wavelengths between 4000 and 5000 angstroms that will give constructive interference. It sounds like your case has and air gap between two plates, and you can assume very small angle.

 

[janrain]

thanks a lot. that helped.