A convex spherical surface with radius r separates a medium with index of refraction 2 from air.As an object in air is moved toward the surface from far away along the central axis, its image:
A)changes from virtual to real when it is a distance r/2 from the surface
B)changes from virtual to real when it is a distance r from the surface
C)changes from real to virtual when it is a distance r/2 from the surface
D)changes from real to virtual when it is a distance r from the surface
E)remains real

Question

Quizplus · Accepted Answer

Since the surface is convex, light will refract away from the central axis and converge at a point closer to the surface than the object. This means that the image will be real. As the object approaches the surface, the image will move further away from the surface due to the convex shape. The image will change from real to virtual when the object is at a distance equal to the focal length of the spherical surface. For a spherical surface, the focal length is given by f = r/2, where r is the radius of the surface. Therefore, the image will change from real to virtual when the object is a distance of r away from the surface. Hence, the correct option is D.

A Convex Spherical Surface with Radius R Separates a Medium