The lens in the figure has a radius of curvature R and is lying on a flat glass
ID: 2252069 • Letter: T
Question
The lens in the figure has a radius of curvature R and is lying on a flat glass block and illuminated from above, Circular interference fringes (called Newton's rings) appear, associated with the variable thickness d of the air film between the lens and the plate. In a particular Newton's rings experiment the radius of curvature of the lens is 6.00 meters and its diameter is 15.57 mm. How many bright rings are produced? Assume incident light with a wavelength of 561.0 nm.
How many bright rings would be seen if the arrangement were immersed in a liquid with a refractive index of 1.31 if the lens and glass block have a refractive index of 1.51?
The lens in the figure has a radius of curvature R and is lying on a flat glass block and illuminated from above, Circular interference fringes (called Newton's rings) appear, associated with the variable thickness d of the air film between the lens and the plate. In a particular Newton's rings experiment the radius of curvature of the lens is 6.00 meters and its diameter is 15.57 mm. How many bright rings are produced? Assume incident light with a wavelength of 561.0 nm. How many bright rings would be seen if the arrangement were immersed in a liquid with a refractive index of 1.31 if the lens and glass block have a refractive index of 1.51?Explanation / Answer
m = [Xm^2 / lambda R] - 1/2
m = [7.785 mm ^2 / 561nm * 6m] - 1/2
m = 18 = 19 full fringes
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lambda f = lambdao / 1.34 = 561 / 1.31 = 428.24 nm
m = [7.785 mm ^2 / 428.24nm * 6m] - 1/2
m = 23.1 = 24 full fringes
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