A convex lens a focal length of 10 cm. At which of the following position should an object be placed so that this convex lens may act as a magnifying glass?

Where should an object be placed in order of to use a convex lens as a magnifying glass?

A convex lens has focal length 5m. At what distance should an object be placed so as to have a real image magnified twice?

A convex lens of focal length f will form a magnified real image of an object if the object is placed

A convex lens has focal length of 30cm. Calculate at what distance should the object be placed from the lens so that it forms at 60 cm on the other side of the lens ? Find the magnification produced by the lens in this case.