Which UV radiation is more harmful due to higher energy and tendency to cause DNA damage?

• A. UV-A
• B. UV-C
• C. UV-B
• D. Visible light

Answer: (C)

Shorter wavelengths have more energy per photon, so UV radiation with higher energy is more capable of breaking chemical bonds in DNA. Among UV bands, UV-C has the most energy, but the atmosphere blocks nearly all of it, so it doesn’t reach us in normal sunlight. UV-B has higher energy than UV-A and is the main band that can directly damage DNA, creating lesions like thymine dimers that can lead to mutations and sunburn. Visible light has even lower energy and is much less likely to cause direct DNA damage. So UV-B is the most harmful in terms of energy and DNA damage under typical exposure.