Newton's ring
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When we put a lens on the glass plate and flash a monochromatic light, pattern with a concentric circle shape appears.
At this time, we can observe the pattern without curvature. This phenomenon is caused by the air layer between the a curved surface of lens and a plain surface of glass. If we flash a monochromatic light vertically on this lens on the glass, reflected light on the surface of lens and reflected light on the surface of glass make an interference and circular pattern. |
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Destructive interference Because the phases of reflected light on the surface of lens and reflected light on the surface of glass are destroyed, the pattern of it become dark. |
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Reinforced interference
Because the phases of reflected light on the surface of lens and reflected light on the surface of glass are reinforced, the pattern of it become light. |
Using the wavelength of light \lambda, curvature radius of lens R, and distance from the center of lens r, we can calculate the intensity of light I as follows;
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I0: intensity of incident light \lambda: wavelength of incident light (m) R: curvature radius of lens (m) r: distance from the center of lens (m) |
where I0 is intensity of incident light.
| This effect is applied to examine the uniformity of curvature of lens. |  |
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Newton ring phenomenon may appear when we scan the film image with a scanner. This is caused by the blank space between the film and the scanner. We can prevent this effect putting the film on the scanner without a blank space. (quotation from Epson Color Guide) |