Vishal − Profile

always the focal length of convex lens is negative and +ve for concave lens 

-100/25+100/10

=+6D

placenta in the embryo gives food and oxygen and removes waste 

chlorine [ne]3s23p5

the diatomic O2 divides into 2 oxygen atoms this is highly exothermic 

it closes the pupil when there is bright light, it opens up pupil when there is low light and allows much amount of light to enter into the eye