Question

how can the sun rays transfer into vitamin D in our body

Answer 1

Ultraviolet-B light strikes the skin where there is a zoosterol called 7-dehydrocholesterol. 7-dehydrocholesterol reacts to the UVB light and converts into Vitamin D3.

Answer 2

what s the meaning of zoosterol ? kind of lipid?

Answer 3

how about ultraviolet-A?

Answer 4

Ultraviolet-A doesn't interact with 7-dehydrocholesterol.
And a zoosterol is a kind of cholesterol precursor.