Light is incident on a glass plate `(mu=1.5)` such that angle of refraction is `60^(@)` dark band is observed corresponding to the wavelength of 6000Å. If the thickness of glass plate is `1.2xx10^(-3)` mm. calculate the order of the interference band.

Explanation

`mu=1.5,r=60^(@),lamda=6000Å=6xx10^(-7)mimpliest=1.2xx10^(-3)=1.2xx10^(-6)m`
`n=(2mutcosr)/(lamda)=(2xx1.5xx1.2xx10^(-6)xxcos60^(@))/(6xx10^(-7))=(2xx1.5xx1.2xx10^(-6)xx(1)/(2))/(6xx10^(-7))=3`