By using a concave mirror, image of a tree is focused on a screen. Prove that the distance between the screen and the mirror is equal to twice the focal length of the concave mirror.

Q. The image of a distant object is obtained on a screen by using a concave mirror. The focal length of the mirror can be determined by measuring the distance between :

Q. To determine the approximate value of the focal length of a given concave mirror, you focus the image of a distance object formed by the mirror on a screen. The image obtained on the screen, as compared to the object is always.

Q. The image of a stone is focussed on a screen using a concave mirror in air. The image is formed at a distance of $20\text{m}$ when the object is kept at a distance of $10\text{m}$. If the mirror is replaced by another mirror of twice the focal length, determine the distance by which the screen has to be moved so that the image is focussed on it.

Q. While determining the focal length of a concave mirror, a student obtained the image of a distant object on a screen. In order to get the focal length of the mirror, the student should measure the distance:
(1) between the object and the mirror only
(2) between the screen and the mirror only
(3) between the object and the screen only
(4) between the screen and mirror as well as between the screen and the object