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versine
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How come when the illumination is from below, the central spot is bright, but when the illumination is from above, the central spot is dark?
Hi sir, could you please explain why shining light from underneath produces a bright spot at the centre?Ibix said:Do you know what causes the rings?
Let's say you are on the other side of the glass from the light. The center of the curved and straight glasses touch. Will you get any reflection at the interface (hint: is it really an interface if two identical materials are in direct contact)?phantomvommand said:Hi sir, could you please explain why shining light from underneath produces a bright spot at the centre?
This is an example of why I love PF so much. Just a few words and no equations to give pretty much the whole story!Ibix said:Let's say you are on the other side of the glass from the light. The center of the curved and straight glasses touch. Will you get any reflection at the interface (hint: is it really an interface if two identical materials are in direct contact)?
Newton's Rings central spot brightness is the brightness of the central spot formed when a convex lens is placed on top of a flat glass surface. This phenomenon is caused by the interference of light waves reflected from the two surfaces, resulting in a bright central spot surrounded by a series of concentric rings.
The central spot brightness is directly proportional to the thickness of the air gap. As the thickness increases, the path difference between the reflected light waves also increases, resulting in a brighter central spot. Conversely, a thinner air gap will result in a dimmer central spot.
Yes, the central spot brightness can be used to determine the refractive index of a material. By measuring the thickness of the air gap and the number of rings surrounding the central spot, the wavelength of the light used, and the radius of curvature of the lens, the refractive index of the material can be calculated using the equation: n = (m+1/2)(λR)^2/t, where n is the refractive index, m is the number of rings, λ is the wavelength, R is the radius of curvature, and t is the thickness of the air gap.
The central spot brightness is dependent on the wavelength of the light source. Light sources with shorter wavelengths, such as blue light, will result in a brighter central spot compared to longer wavelengths, such as red light. This is because the path difference between the light waves is greater for shorter wavelengths, resulting in more constructive interference and a brighter central spot.
The central spot appears dark when a concave lens is used because the light waves reflected from the two surfaces are now out of phase, resulting in destructive interference and a dark central spot. This is because the concave lens causes the reflected light waves to diverge, rather than converge as in the case of a convex lens.