convex lenses are used in the human eye to help focus light onto the retina, allowing us to see clearly. The natural lens in the human eye is flexible and can change its shape, allowing it to adjust the focal length and focus on objects at different distances. This process is called accommodation and is essential for clear vision.

female sterilization is commonly referred to as tubectomy. Tubectomy is a surgical procedure in which a woman's fallopian tubes are blocked, cut, or sealed to prevent eggs from reaching the uterus for fertilization. This method of permanent contraception is also known as tubal ligation.

The Agni missile is a family of medium to intercontinental range ballistic missiles developed by India, named after one of the five elements of nature. The first missile of the series, Agni-I was developed under the Integrated Guided Missile Development Programme and tested 1991.