What is meant by power of a lens? Write its SI unit. A student uses a lens of focal length 40 cm and another of -20 cm . Write the nature and power of each lens.

What is meant by power of a lens ? Write its Sl unit. A student uses a lens of focal length 40 cm and another of - 20 cm. Write the nature and power of each lens.

Define power of a lens. What is its unit ? One student uses a lens of focal length 50 cm and another of - 50 cm . What is the nature of the lens and power used by each of the them ?

Define power of a lens. What is its unit ? One student uses a lens of focal length 50 cm and another of - 50 cm . What is the nature of the lens and its and power used by each of the them ?