An object is kept at a distance of 10 cm from a concave mirror of focal length 5 cm, the magnitude of the image is
Less than 10 cm
More than 10 cm
Equal to 10 cm
Can’t calculate with the given data
When an object of height 1 cm is kept at a distance of 4 cm from a concave mirror, its upright image of height 1.5 cm is formed at a distance of 6 cm behind the mirror. Calculate the focal length of the mirror(only magnitude) ___