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Questions
Write the new Cartesian sign convention for spherical lenses.
State and explain the New Cartesian Sign Convention for spherical lenses.
Explain the Cartesian sign convention used for the lens.
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Solution
New Cartesian Sign Convention for Spherical Lenses: The new Cartesian sign convention is used for measuring various distances in the ray diagrams of lenses.
According to this convention:
- The object is always placed on the left of the lens; i.e., light must fall on the lens from left to right.
- All distances parallel to the principal axis are measured from the optical centre of the lens.
- The distances along the direction of incident rays (along the positive x-axis) are taken as positive, whereas the distances opposite to the direction of incident rays (along the negative x-axis) are taken as negative.
- Distances measured above the principal axis (along the positive y-axis) are taken as positive.
- Distances measured below the principal axis (along the negative y-axis) are taken as negative.
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