A concave mirror has A a positive or negative focal length d

A concave mirror has A. a positive or negative focal length depending on the object position. B. a positive focal length. C. a positive or negative focal length depending on the object size. D. no focal length. E. a negative focal length.

Solution

Consider incoming, incident rays of light that are parallel to the Optic Axis. You may think of these as rays of light from an object infinitely far away, an infinitly far distant object.

When these rays strike a concave mirror, they are reflected so they go through a common point and then go on their way; this point is called the focal point. The distance from the mirror to the focal point F is called the focal length and is labeled f. The focal length f is positive for a concave mirror.