Answer:
A concave lens is thinner in the middle and thicker at the edges. A convex lens is thicker in the middle and thinner at the edges. Used in the camera, overhead projector, projector microscope, simple telescope, magnifying glasses, etc. It is also used for the correction of the problem in long sight.
or
The sperm enters the body through the vagina, then travels through the cervix and womb to the fallopian tubes, where the egg is usually fertilised (conception). The egg can be fertilised by sperm contained in semen or pre-ejaculate.