Question:

11. A real image of a distant object is formed by a planoconvex lens on its principal axis. Spherical aberration

Updated On: Jan 18, 2023
  • is absent
  • is smaller if the curved surface of the lens faces the object
  • is smaller if the plane surface of the lens faces the object
  • is the same whichever side of the lens faces the object
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The Correct Option is B

Solution and Explanation

In general spherical aberration is minimum when the total
deviation produced by the system is equally divided on all
refracting surfaces. A planoconvex lens is used for this
purpose. In order that the total deviation be equally divided
on two surfaces, it is essential that more parallel beam (or the
incident and refracted) be incident on the convex side. Thus,
when the object is far away from the lens, incident rays will
be more parallel than the refracted rays, therefore, the object
should face the convex side,but if the object is near the lens,
the object should face the plane side. This has been shown in
figure.
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Concepts Used:

Spherical Lenses

Lenses that are made by combining two spherical transparent surfaces are called spherical lenses.  In general, there are two kinds of spherical lenses. Lenses that are made by joining two spherical surfaces that bulge outward are convex lenses, whereas lenses that are made by joining two spherical surfaces that curve inward are concave lenses.

Properties of Convex lens:

  1. In this, the lenses are thicker in the middle and thinner at the edges.
  2. They have a positive focal length.
  3. It intersects the incident rays towards the principal axis
  4. These lenses are used in the camera, focus sunlight, projector microscope, simple telescope, overhead projector, magnifying glasses, etc.

Properties of Concave lens:

  1. These lenses are thinner in the middle and thicker at the edges.
  2. They have a negative focal length.
  3. It parts the incident rays away from the principal axis.
  4. These are used in the glasses, spy holes, some telescopes in the doors, etc.