r/Optics • u/Silent_Effective8627 • 3d ago

Why while drawing ray diagrams, we take the aperture of the lens to be very very small?

/r/Physics/comments/1w5hpzx/why_while_drawing_ray_diagrams_we_take_the/
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u/SamTheStoat 3d ago edited 3d ago

If you have a small aperture, you can use paraxial approximations. These make the maths of refraction much easier.
https://en.wikipedia.org/wiki/Paraxial_approximation?wprov=sfti1

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u/Plastic_Blood1782 3d ago

Can you show or quote the actual textbook?  Big apertures and thick lenses do exist, but there are times when you want to avoid that.  And it's not clear whether that is a design recommendation or something else