Do we need any assumption when using Newton ring's formula ?

In summary, the conversation discusses the equation 2t=nλ and the variables t, n, and λ. The question is which diagram is correct, with one participant suggesting that the vertically down and up diagram is correct but the other suggesting that the other diagram may be wrong due to the incident angle being different. The conversation also briefly mentions a pattern where there is no reflection due to the surfaces being in intimate contact, leading to a question about the meaning of "no surface."
  • #1
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Homework Statement


2t=nλ, t=thickness , n=the number of rings counted, λ=wavelength.
Which diagram is correct?



Homework Equations





The Attempt at a Solution


I think the vertically down and up is correct for the using 2t=nλ, but the curved surface should make the incident angle different with the angle of the reflected ray . If so, the other diagram should be wrong unless we can make the reflected light(glass) must be parallel with the reflected light(lenses) .

please help , thank you
 

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  • #2
The center of the pattern is black. Here the two glass surfaces are in intimate contact and there is no reflection because it is as if there were no surface.
What is the meaning of no surface??
 

FAQ: Do we need any assumption when using Newton ring's formula ?

1. What is Newton's ring formula and how is it used?

Newton's ring formula is a mathematical equation that calculates the spacing between the concentric rings formed by the interference of light waves reflected from a convex lens and a flat glass surface. It is used to determine the radius of curvature of the lens and the thickness of the thin film of air between the lens and the glass surface.

2. Why is an assumption necessary when using Newton's ring formula?

An assumption is necessary when using Newton's ring formula because it is based on several simplifying assumptions, such as the lens being perfectly spherical and the light waves being monochromatic. These assumptions may not hold true in all cases, which can result in inaccuracies in the calculated values.

3. What happens if the assumptions are not met?

If the assumptions are not met, the calculated values obtained from Newton's ring formula may not be accurate. This can be due to factors such as the lens not being perfectly spherical, the light source emitting multiple wavelengths, or the presence of impurities on the glass surface. In such cases, the formula may need to be modified or other methods may need to be used to obtain more accurate results.

4. Can Newton's ring formula be used for all types of lenses?

No, Newton's ring formula is specifically designed for measuring the curvature of convex lenses. It cannot be used for concave lenses or other types of lenses, such as cylindrical lenses. Different formulas and methods are required for measuring the properties of these lenses.

5. Are there any limitations to using Newton's ring formula?

Yes, there are certain limitations to using Newton's ring formula. It is only applicable for thin lenses and cannot be used for thick lenses. Additionally, the formula assumes that the lens and glass surface are in perfect contact, which may not always be the case. It is important to consider these limitations when using the formula to ensure accurate results.

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