Which type of UV radiation is known as the "burning ray"?

The "burning ray" refers specifically to UVB radiation. This type of ultraviolet radiation has a shorter wavelength than UVA and is primarily responsible for causing sunburn, which can lead to skin damage. UVB rays penetrate the outer layer of the skin, triggering a biological response that results in the production of melanin, which causes the skin to darken. However, excessive exposure to UVB can have harmful effects, including the development of skin cancer.

UVA radiation, while more prevalent and capable of penetrating deeper into the skin, is more associated with skin aging and the breakdown of collagen rather than immediate burning. UVC radiation does not typically reach the earth's surface due to absorption by the atmosphere and is not known for burning. The term "UVD" is not commonly recognized in the context of UV radiation types. Hence, UVB is correctly identified as the "burning ray" due to its direct impact on the skin's surface and its role in causing sunburn.