# Newton's Rings: Darker or Brighter Central Spot?

• oreo

#### oreo

If light is transmitted at a point of contact in Newton's rings. The central spot will be darker or brighter?

If you understand how Newtons rings are formed, what do you think and why?

CWatters said:
If you understand how Newtons rings are formed, what do you think and why?
Actually I can't understand what the word "transmission at contact point" here means. I know that there is thin layer of air at contact point due to which there is phase shift of 180° which results in dark point at mid.

## 1. What are Newton's Rings?

Newton's Rings are a set of concentric, alternating light and dark rings that are observed when a plano-convex lens is placed on top of a flat glass surface with a thin layer of air in between.

## 2. Why is there a central spot in Newton's Rings?

The central spot in Newton's Rings is caused by the interference of light waves that are reflected from the top and bottom surfaces of the thin air layer between the lens and the glass surface. This results in a constructive interference at the center, producing a brighter spot.

## 3. Can the central spot change in brightness?

Yes, the central spot can change in brightness depending on the thickness of the air layer between the lens and the glass surface. If the air layer becomes thicker, the central spot will become darker. If the air layer becomes thinner, the central spot will become brighter.

## 4. What factors can affect the appearance of Newton's Rings?

The appearance of Newton's Rings can be affected by the quality of the lens and glass surface, the thickness of the air layer, the color of the light source, and the angle of incidence of the light on the surfaces.

## 5. What are some practical applications of Newton's Rings?

Newton's Rings have practical applications in measuring the flatness of surfaces, testing the quality of lenses, and determining the thickness of very thin films. They are also used in the design and calibration of optical instruments and devices.