Final answer:
Vitamin D is the fat-soluble vitamin produced in the skin when exposed to UV radiation; it is vital for calcium and phosphorous absorption, critical for bone health.
Step-by-step explanation:
The vitamin that is fat-soluble, produced in the skin on exposure to UV radiation, and necessary for normal bone growth and function is Vitamin D. When the human skin is exposed to UV radiation, particularly UVB rays, it synthesizes Vitamin D. This process involves the conversion of a cholesterol derivative in the skin to a form of Vitamin D3 known as cholecalciferol. This is further processed in the liver into calcidiol and then in the kidneys into calcitriol, the active form of Vitamin D. This vitamin is essential for the absorption of calcium and phosphorous, which are critical for maintaining healthy bones. Without adequate sun exposure or dietary intake, one could suffer from conditions such as rickets in children, characterized by bone deformities and bowleggedness, or osteomalacia in adults, leading to softened bones.