Two concave refracting surfaces of equal radii of curvature and refractive index face each other in air as shown in figure. A point object O is placed midway, between P and B. The separation between the images of O, formed by each refracting surface is:
Correct answer:B
Standard Method
Given: Two concave refracting surfaces have equal radius of curvature and refractive index . The object is placed midway between and .
Find: The separation between the images formed by the two refracting surfaces.
From the solution, the result is stated using the spherical refracting surface relation.
The extracted working on the solution's is internally compressed and does not show intermediate derivation steps clearly, but it concludes that the separation is:
Therefore, the separation between the images of is . The correct option is B.
Using the thin lens formula instead of the refraction formula for a spherical surface is incorrect because each boundary acts as a refracting surface, not a complete lens. Use the spherical refracting surface relation for each surface separately.
Ignoring the sign convention for a concave refracting surface gives the wrong image position. Assign the radius of curvature and object distance with the proper signs before substituting.
Assuming both images form at equal distances from the midpoint without calculation is incorrect. Find the image due to each refracting surface first, then take their separation.
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