Q.
A transparent sphere of radius R and refractive index μ is kept in air. At what distance from the surface of the sphere should a point object be placed so as to form real image at the same distance from the sphere?
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Ray Optics and Optical Instruments
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Solution:
As P1O=P2I, therefore, the rays must pass through the sphere in a direction parallel to the optic axis, as shown in the figure.
Now, for first refraction at A from rarer to denser medium, −uμ1+vμ2=Rμ2−μ1 ⇒−u1+∞μ=Rμ−1 ∴u=−(μ−1)R
or ∣u∣=(μ−1)R