Question

Could you please explain ray tracing for mirrors, how do you know which way the traces go and why, I'm having trouble figuring out where the object is vs. the image. Thank you

Answer 1

When a point object is placed before a spherical mirror of small aperture, a point image is formed. To locate the position of the image, we draw two rays from the point object, make them incident on the mirror and trace the reflected rays. The line joining the point of incidence and the center of curvature is the normal. A reflected ray is traced by applying the laws of reflection. If the reflected rays intersect, the point of intersection is the real image. If the rays diverge after reflection a virtual image is formed at the point from where the rays seem to diverge. Below Figure shows some examples.

If the incident rays diverge from a point object, the object is called a real object. Sometimes the rays incident on the mirror do not diverge from a point, rather they converge towards the mirror as shown in figure(c). In this case, the point where these rays would meet if there were no mirror, is treated as the object. Such a point is called a virtual object.

General rules helpful in tracing-

Any ray of light that passes through the mirror always passes through the principal focus (f) of the mirror after reflection.

A ray of light passing through the center of curvature of any mirror is reflected back along the same path.