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two identical thin Plano convex glass of refractive index 1.5 each having radius of curvature 20 cm are placed with their convex surfaces at the centre the intervening surface is filled with oil of refractive index 1.7 ,the focal length of the combination is
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two identical thin Plano convex glass of refractive index 1.5 each hav...
Calculation of Focal Length of the Combination of Two Plano-Convex Glass Lenses


Given:


  • Refractive index of each lens, n1 = 1.5

  • Radius of curvature of each lens, R = 20 cm

  • Refractive index of oil, n2 = 1.7



Formula used:

The formula used to calculate the focal length of the combination of two lenses is:

1/f = (n2 - n1) * (1/R1 + 1/R2 - d/(n1 * n2 * R1 * R2))

where

R1 = R2 = R (radius of curvature of each lens)

d = distance between the two lenses (thickness of the oil layer)

Calculation:

Given, R = 20 cm

Let the thickness of the oil layer be d cm

Using the formula for the focal length of the combination of two lenses:

1/f = (n2 - n1) * (1/R1 + 1/R2 - d/(n1 * n2 * R1 * R2))

1/f = (1.7 - 1.5) * (1/20 + 1/20 - d/(1.5 * 1.7 * 20 * 20))

1/f = 0.2 * (1/10 - d/1020)

1/f = 0.02 - 0.0002d

f = 50 - 5d (taking reciprocal both sides)

Result:

The focal length of the combination of two identical thin plano-convex glass lenses of refractive index 1.5 each having a radius of curvature 20 cm placed with their convex surfaces at the centre, the intervening surface filled with oil of refractive index 1.7 is 50 - 5d cm.
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Read the following text and answer the following questions on the basis of the same:Negative Refractive Index: One of the most fundamental phenomena in optics is refraction. When a beam of light crosses the interface between two different materials, its path is altered depending on the difference in the refractive indices of the materials. The greater the difference, the greater the refraction of the beam. For all known naturally occurring materials the refractive index assumes only positive values. But does this have to be the case?In 1967, Soviet physicist Victor Veselago hypothesized that a material with a negative refractive index could exist without violating any of the laws of physics.Veselago predicted that this remarkable material would exhibit a wide variety of new optical phenomena. However, until recently no one had found such a material and Veselago’s ideas had remained untested. Recently, meta-material samples are being tested for negative refractive index. But the experiments show significant losses and this could be an intrinsic property of negativeindex materials.Snell’s law is satisfied for the materials having a negative refractive index, but the direction of the refracted light ray is ‘mirror-imaged’ about the normal to the surface.There will be an interesting difference in image formation if a vessel is filled with “negative water” having refractive index – 1.33 instead of regular water having refractive index 1.33.Say, there is a fish in a vessel filled with negative water. The position of the fish is such that the observer cannot see it due to normal refraction since the refracted ray does not reach to his eye.But due to negative refraction, he will be able to see it since the refracted ray now reaches his eye.Q. A ray incident on normal glass and “negative glass” at an angle 60°. If the magnitude of angle of refraction in normal glass is 45° then, what will be the magnitude of angle of refraction in the “negative glass”?

two identical thin Plano convex glass of refractive index 1.5 each having radius of curvature 20 cm are placed with their convex surfaces at the centre the intervening surface is filled with oil of refractive index 1.7 ,the focal length of the combination is
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two identical thin Plano convex glass of refractive index 1.5 each having radius of curvature 20 cm are placed with their convex surfaces at the centre the intervening surface is filled with oil of refractive index 1.7 ,the focal length of the combination is for Class 12 2024 is part of Class 12 preparation. The Question and answers have been prepared according to the Class 12 exam syllabus. Information about two identical thin Plano convex glass of refractive index 1.5 each having radius of curvature 20 cm are placed with their convex surfaces at the centre the intervening surface is filled with oil of refractive index 1.7 ,the focal length of the combination is covers all topics & solutions for Class 12 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for two identical thin Plano convex glass of refractive index 1.5 each having radius of curvature 20 cm are placed with their convex surfaces at the centre the intervening surface is filled with oil of refractive index 1.7 ,the focal length of the combination is.
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