Newton’s Rings Experiment

The key idea behind the Newton’s Rings experiment is the thin film formation between plane-convex lens and glass plate. Due to this thin film of air a path difference occurs in the waves which reflect from the lower surface of the lens and the top surface of the glass plate. As a result of it, they superimpose and develop the interference pattern. The intensity depends on the nature of the pattern means it is constructive or destructive.

Here some questions are asked to make experiment working more clear in terms of physical concepts. If you find difficult to give the answer of any question you can ask through comment box of this post.

1Q. What is the superposition principle?

2Q. What do you mean by an interference of two or more than two waves?

3Q. What is the relation between path difference and phase difference?

4Q. When two waves interfere the intensity distribute uniformly. How do you see the output of intensity distribution as a result of interference?

5Q. Why do you use the plane-convex lens?

6Q. What is the approximate focal length of the plano-convex lens?

7Q. How do you obtain thin film and what is the role of it?

8Q. Can a thin film be off the air?

9Q. Is it true that only through the monochromatic light you can observe Newton‘s ring?

10Q. Alright, the thin film which developed here is of uniform thickness or it gradually decreases towards the center, where plane-convex lens (its convex surface is placed) and glass plate contacts.

11Q. Why do you put thin glass plate at 45 degrees to the light source?

12Q. The circular ring formed of various diameters in this experiment. This is the result of light reflection from upper and lower surfaces or is a result of the refraction?

13Q. Here you observe dark and bright circular rings through the eyepiece, the reason behind of it is a monochromatic source or interference conditions?

14Q. How you can determine the wavelength of a monochromatic source by using this experiment in which you just observe the diameter and number of the rings? Is there any formula for wavelength determination?

15Q. What do you understand from the least count of any measuring device?

16Q. Can you determine the radius of curvature of a spherical surface from this experiment? Is there any formula for this purpose?

17Q. What type of relationship do you see between diameter and number of rings? Are they directly proportional or inversely proportional?

18Q. Where do you can use this experiment? What are the possible applications?