Solution to task 508 from Chertov´s for extramural stud

Solution to task 508 from Chertov´s for extramural stud

508. A plano-convex glass lens with f = 1 m lies with its convex side on a glass plate. The radius of the fifth dark Newton ring in reflected light is r5 = 1.1 mm. Determine the light wavelength λ.