Help with Newton's Rings Homework Questions

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In summary, the conversation is about a Newton's Ring experiment and the questions related to it. The experiment involves a planoconvex glass lens with a diameter of 14.3 cm and a refractive index of 1.54. The questions include the thickness of the lens, the radius of curvature of the convex surface, and the focal length of the lens. The individual asking for help has attempted to use the formulae but has not been able to get the correct answers. They are seeking assistance in understanding and solving the problem.
  • #1
Knicks685
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Hi. I have some homework questions here that I need a little help on. I know the fomulae to use just do not know how to apply it properly. Any help will be appreciated.

In a Newton's Ring experiment, a planoconvex glass (n=1.54) lens having a diameter 14.3 cm is placed on a flat plate. When 585 nm light is incident normally, 8 bright rings are observed with the last one right on the edge of the lens, at r.

1. What is the thickness of the lens?
2. What is the radius of curvature of the convex surface of the lens?
3. What is the focal length of the lens?
 
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  • #2
not that i can answer this but if you read the FAQ you are supposed to show some working or some effort to have started your problem, maybe if you do that you will have more of a chance of it being answered
 
  • #3
Well I know that at the center there is a dark spot so to find the thickness of the lens I'd assume that t=m(lambda)/2n but I get an unreasonable answer. To find the radius of curvature I tried using r=sqroot(m(lambda)R/n therefore R=r^2/(m*lambda*n) but again I don't think I'm getting the right answer. I'm not trying to catch a break here. So any help will be appreciated.
 

1. What are Newton's Rings?

Newton's Rings are a series of concentric colored rings that appear when a convex lens is placed on top of a flat glass surface. They were first observed by Sir Isaac Newton in the 18th century.

2. How are Newton's Rings formed?

Newton's Rings are formed due to the interference of light waves that are reflected from the curved surface of the convex lens and the flat surface of the glass. This interference creates a pattern of light and dark rings.

3. What is the significance of Newton's Rings?

Newton's Rings are important in the study of optics as they demonstrate the principles of interference and diffraction of light. They also have practical applications in the manufacturing of lenses and other optical instruments.

4. How can I calculate the radius of curvature using Newton's Rings?

The radius of curvature can be calculated using the formula R = (m+1/2)λR, where m is the number of the dark ring, λ is the wavelength of light used, and R is the radius of curvature of the convex lens.

5. How can I determine the wavelength of light using Newton's Rings?

To determine the wavelength of light, you can use the equation λ = d(m+1/2)/nR, where d is the distance between the lens and glass surface, m is the number of the dark ring, n is the refractive index of the medium, and R is the radius of curvature of the convex lens.

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