14. (3 points) A concave mirror and a double convex lens (both are converging op

Question

14. (3 points) A concave mirror and a double convex lens (both are converging optics) each double convex lens (both are converging optic) each have a focal length of 1.5 meters in air. Now they are both submerged in water and the focal lengths are measured again. What should be expected from the new focal lengths? A. Both focal lengths are unchanged B. Both focal lengths are longer C. Both focal lengths are shorter D. The focal length is longer for the lens but shorter for the mirror E. The focal length is longer for the lens but unchanged for the mirror

Explanation / Answer

here,

Focal length of any mirror (concave) does not depend on medium, so it remains unchanged.

If refractive index of the material of convex lens is greater than that of water, then its focal length will increase.

If refractive index of the material of convex lens is equal to that of water,
then its focal length will become infinity.

If refractive index of the material of convex lens is less than that of water,
then its focal length will become negative i.e it will behave like concave lens

(E) the new focal length is longer for the lens and unchanged for the mirror

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