An equiconvex lens is placed on another equiconvex lens. The radii of curvatures of the two surfaces of the upper lens are $R_1$ and those of the lower lens are $R_2$. The waves reflected from the upper and lower surface of the air film (formed between the two lenses) interfere to produce Newton's rings. Calculate the radii of the dark rings.
Can anyone please help me with the Ray diagram and geometry in this case , I am unable to understand it . I do want the answer, just want to understand the Ray diagram and geometry then I will try it. I was thinking of treating the two surface of air film as convex and concave mirror but for $R_1$$R_2$ it's getting difficult to draw the diagram. So please help.

  • $\begingroup$ Any help please... $\endgroup$ – User 1 May 11 at 8:00
  • $\begingroup$ Hint - start by following the raytraces in the standard situation, en.wikipedia.org/wiki/Newton%27s_rings . Then use trace rays down to the second lens' top surface, apply Snell's law, etc. $\endgroup$ – Carl Witthoft May 11 at 14:25

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