# Newton's Rings using refractive index of water

• emmalou
In summary, the conversation discusses the use of water as a replacement for air in an experiment involving Newton's Rings. The individual has found that the rings are extremely faint and wonders if anyone knows the cause or solution. They confirm that they put the water between the curved and plane surfaces and explain their setup with a planeo-convex lens, glass slide at 45 degrees, and a sodium lamp. The expert suggests that by replacing air with water, the intensity of the reflected light is decreased, and the rings may be harder to see due to the slower speed of light in water. They ask about the expected results if the water is replaced with glass of the same index as the lens and slide.
emmalou
Hi

I am currently looking at Newtons Rings, i have changed my refractive index to water (distilled), i have found the rings and they seem to be as aspected except they are extremely faint barely readable infact would anyone know a cause or soulation to this?

It's hard to say without more detail of your experiment.
What index did you changed to water? Or of what?
Did you put water between the curved surface and the plane surface?

nasu said:
It's hard to say without more detail of your experiment.
What index did you changed to water? Or of what?
Did you put water between the curved surface and the plane surface?

i changed the index from air to water to see the affects, yes i did byt it between the curved surface and the plane surface.

The lense i am using is a planeo-convex lens and i have my glass slide at 45 degrees my lamp is also a sodium!
this is a picture of my set up

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Well, by replacing air with water you decrease the intensity of the reflected light at both interfaces.
The reflection coefficient depends on the difference between the indices. If you reduce the difference more light will just get through, without being reflected.

What would you expect if you replace the water with glass of the same index as the lens and slide (without any air at the interface)?

emmalou said:
i changed the index from air to water to see the affects, yes i did byt it between the curved surface and the plane surface.

The lense i am using is a planeo-convex lens and i have my glass slide at 45 degrees my lamp is also a sodium!
this is a picture of my set up
As the light travels slower in the water, it is equivalent to having a bigger gap, and so the rings will be more closely spaced and harder to see.

## 1. What are Newton's Rings?

Newton's Rings are a series of concentric, colored rings that appear when a plano-convex lens is placed on top of a flat glass surface. They are caused by the interference of light waves as they reflect off of the two surfaces.

## 2. How are Newton's Rings formed using the refractive index of water?

When a plano-convex lens is placed on top of a flat glass surface that has a thin layer of water in between, the light waves passing through the water and reflecting off the two surfaces create Newton's Rings. The refractive index of water affects the thickness of the water layer, which in turn affects the spacing of the rings.

## 3. What is the significance of using the refractive index of water in this experiment?

The refractive index of water is an important factor in this experiment because it affects the thickness of the water layer, which ultimately determines the spacing of the Newton's Rings. By varying the refractive index, different patterns of rings can be observed, providing valuable information about the properties of the materials used.

## 4. How does the refractive index of water affect the appearance of Newton's Rings?

The refractive index of water affects the spacing of the rings, with a higher refractive index resulting in closer spacing and a lower refractive index resulting in wider spacing. This can also alter the colors of the rings, as different colors have different wavelengths and are affected differently by changes in refractive index.

## 5. What applications does the study of Newton's Rings using the refractive index of water have?

The study of Newton's Rings has various applications in the fields of optics and materials science. It can be used to measure the refractive index of liquids, study the properties of thin films, and even detect small imperfections on surfaces. It is also a common experiment in physics and optics courses to demonstrate the principles of light interference and wave behavior.

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