For the Fabry-Perot etalon of thickness `d = 2.5 cm` find:
(a) the highest order of interference of light with wavelength `lambda = 0.50 mu m`,
(b) the dispersion region `Delta lambda`, i.e the spectral interval of wavelengths, within which there is still no overlap with orders of interference if the observation is carried out appoximately at wavelength `lambda = 0.50 mu m`.

Explanation

(a) We have `k_(max) = (2d)/(lambda).` for `theta = 0. = 10^(5)`.
(b) We must have
`2d cos theta = k lambda = (k - 1) (lambda + Delta lambda)`
Thus `(1)/(k) = (lambda)/(2d)`. and `Delta lambda = (lambda)/(k) = (lambda^(2))/(2d) = 5pm`. On putting the values.