# WHY NEWTON RINGS ARE CIRCULAR

## WHY NEWTON RINGS ARE CIRCULAR

Newton rings are circular patterns that appear when light reflects off two closely spaced surfaces. The colors of the rings are determined by the thickness of the air gap between the surfaces. This phenomenon is named after Sir Isaac Newton, who first described it in 1717.

## How Newton Rings are Formed

To observe Newton rings, one can place a slightly curved glass surface on top of a flat glass surface. When light is shone through the glass, the light waves reflect off the two surfaces of the glass. The reflected waves interfere with each other, creating a pattern of light and dark rings.

The center of the rings is dark because the light waves that reflect off the two surfaces are in phase with each other. This means that the waves reinforce each other, creating a bright spot. As you move away from the center, the light waves gradually become out of phase with each other. This results in a series of alternating bright and dark rings.

### Factors Affecting Newton Ring Formation

• Air Gap Thickness: The thickness of the air gap between the two glass surfaces is the primary factor that determines the size and spacing of Newton rings. A thicker air gap will result in larger rings, while a thinner air gap will produce smaller rings.
• Wavelength of Light: The wavelength of the light that is used to illuminate the Newton rings also affects their appearance. Shorter wavelengths (i.e., blue light) will produce smaller rings than longer wavelengths (i.e., red light).
• Angle of Incidence: The angle at which the light strikes the glass surfaces also affects the shape of the Newton rings. A more direct angle of incidence will produce circular rings, while an oblique angle will produce elliptical rings.

## Applications of Newton Rings

Newton rings have a variety of applications, including:

• Non-Destructive Testing: Newton rings can be used to detect flaws in transparent materials such as glass and plastic. A flaw in the material will cause the Newton rings to become distorted, which can be detected with a trained eye.
• Surface Metrology: Newton rings can be used to measure the surface roughness of a material. The size and shape of the rings can be used to determine the height of the surface features.
• Optical Coatings: Newton rings can be used to design and manufacture optical coatings. These coatings are used to reduce reflection and increase the transmission of light through optical components.

## Conclusion

Newton rings are a beautiful and fascinating phenomenon that has a wide range of applications. The circular shape of the rings is due to the interference of light waves that reflect off two closely spaced surfaces.

## FAQs

1. What causes Newton rings?
2. Newton rings are caused by the interference of light waves that reflect off two closely spaced surfaces.

3. What factors affect the appearance of Newton rings?
4. The thickness of the air gap between the surfaces, the wavelength of the light, and the angle of incidence all affect the appearance of Newton rings.

5. What are some applications of Newton rings?
6. Newton rings are used in non-destructive testing, surface metrology, and optical coatings.

7. Why are Newton rings circular?
8. Newton rings are circular because the light waves that reflect off the two surfaces interfere with each other in a circular pattern.

9. How can Newton rings be used to measure the thickness of a thin film?
10. Newton rings can be used to measure the thickness of a thin film by measuring the spacing between the rings.