# The number of cardinal points in a thick lens is:

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The number of cardinal points in a thick lens is:
1. zero
2. two
3. three
4. six

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Correct Answer - Option 2 : two

Concept:

• Cardinal Point: The cardinal points consist of three pairs of points located on the optical axis of a rotationally symmetric, focal, optical system.
• These are the focal points, the principal points, and the nodal points.
• For ideal systems, the basic imaging properties such as image size, location, and orientation are completely determined by the locations of the cardinal points; in fact, only four points are necessary: the focal points and either the principal or nodal points.
• The only ideal system that has been achieved in practice is the plane mirror, however, the cardinal points are widely used to approximate the behaviour of real optical systems.
• Cardinal points provide a way to analytically simplify a system with many components, allowing the imaging characteristics of the system to be approximately determined with simple calculations.

Explanation:

• As in the thick lense, there are two cardinal points:
• Nodal point
• Center point
• However, the thin lens consists of 6 cardinal points respectively.