Modified Newton's rings: II

TL;DR

This paper extends the Modified Newton's rings experiment by deriving a general wavelength formula applicable at any observation distance and employs video analysis software to distinguish interference fringes.

Contribution

It introduces a generalized wavelength formula for Modified Newton's rings and demonstrates the use of video analysis software for fringe analysis.

Findings

Derived a universal wavelength formula for any observation distance.

Established a relation between focal length and radius of curvature for a plano-convex lens.

Successfully distinguished interference fringes using video analysis software.

Abstract

In an earlier work (Shankar kumar Jha, A Vyas, O S K S Sastri, Rajkumar Jain & K S Umesh, 'Determination of wavelength of laser light using Modified Newton's rings setup', Physics Education, vol. 22, no.3, 195-202(2005)) reported by our group, a version of Newton's rings experiment called Modified Newton's rings was proposed. The present work is an extension of this work. Here, a general formula for wavelength has been derived, applicable for a plane of observation at any distance. A relation between the focal length and the radius curvature is also derived for a plano-convex lens which is essentially used as a concave mirror. Tracker, a video analysis software, freely downloadable from the net, is employed to analyze the fringes captured using a CCD camera. Two beams which give rise to interference fringes in conventional Newton's rings and in the present setup are clearly distinguished.