Question

a concave mirror has a focal length of 2 metre in vaccum. what would be its focal lenth when used in a medium of refractiv index 2.759

Answer 1

Answer:

Explanation:

The focal length is unchanged, provided the image and object planes, as well as the mirror surface, are all immersed in the same media. Think about it this way—if you have a point source located at the center of curvature of the mirror (the focal length being one-half the radius of curvature), an image will be superimposed right on top of the source because all light traveling from the source hits the surface of the mirror at normal incidence and bounces straight back, regardless of the index of the medium between the source and and the mirror surface.