Revisiting Fizeau's observations: Spectral study of Na source using Newton's rings

K S Umesh, Denny Melkay, J Adithya, Sai Prem Shaji, N Ganesh, R Dharmaraj, Rajkumar Jain, S Nanjundan

Sri Sathya Sai Institute of Higher Learning, Physics Department, Brindavan Campus

Conventional Newton’s rings experiment is generally used in undergraduate laboratory to determine the average wavelength of Na doublet. A minor modification of this setup enables us to view simultaneously Newton’s rings both in reflected as well as transmitted light. A movable glass plate with respect to the plano-convex lens allows us to observe the variation of contrast/visibility of these fringes and thus allows us to determine the separation of the Na yellow doublet.