Question

Jasnoor ask his teacher, does focal length of a lens change on changing object distance? What will be the answer of teachers?​

Answer 1

Answer:

No, the focal length of a lens depends only on the curvatures of lens surfaces (their radius) and the lens material (refractive index).

Thus the focal length of a thin lens (simplified formula) is

where, f is the focal length, n equal the refraction index, and r1 and r2 the radius of curvature of each surface.

The focal length of a group lenses depends only on focal length of each lens and their relative position.

Answer 2

Find: Is focal length of a lens change on changing an object distance?

Solution: No, focal length of a lens does not change on changing the position or distance of an object because focal length is the half distance of the radius of the lens. In other words it is half of the length from the curvature to the pole of the lens.

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