When the object is at a distance of more than 6 metres, at that time

An object is kept at a distance more than twice the focal length (F) from a concave mirror. The distance the image formed will be

A man cannot see objects distinctly at a distance less than 1 metre. He is suffering from

A person can not see the objects clearly placed at a distance more than 40 cm . He is advised to use a lens of power

An object is placed at a distance of 10 cm from a concave mirror. When the distance of object from the mirror is decreased to 6 cm, the image gets 2 times magnified than that in first case. Calculate the focal length of the mirror.