Find the nature and power of a lens of focal length + 50 cm.

State whether the following statements are True (T) or False (F): The power of a lens is 4D. The focal length is 50 cm.

Calculate the magnifying power of a magnifier of focal length 2.5 cm.

Find the effective power and focal length of two lenses of focal lengths 50 cm and -200 cm when put in contact. What is the nature of the combined lens?