Image Formation by Concave Mirror

A mirror, in which the reflecting surface curves inwards, is called a concave mirror. A concave mirror converges the light rays from an object to form its image. The properties of the image formed by a concave mirror depend on the position of the object with respect to the mirror. When the object is within the focus of the concave mirror, the image formed is erect, virtual and magnified and is located behind the mirror. A virtual image can only be viewed in the mirror and cannot be projected on a screen. The image formed is magnified and it is because of this reason that concave mirrors are many times used as shaving mirrors. Other practical applications of concave mirrors are car headlights and the astronomical telescope. All large telescopes use a large concave mirror at the bottom of the telescope to gather light and form a small image on a small plane mirror at the top. The purpose of the plane mirror is simply to reflect the light into the eyepiece of the telescope.