Question

which type of uv radiation is the least energetic, and thus, least harmful? uv - a uv - d

Explanation:

UV - A has the longest wavelength among common UV types. According to the formula \(E = h\frac{c}{\lambda}\) (where \(E\) is energy, \(h\) is Planck's constant, \(c\) is the speed of light, and \(\lambda\) is wavelength), longer wavelength means lower energy. Since UV - D is not a standard type of UV radiation (the main types are UV - A, UV - B, and UV - C), and UV - A has lower energy compared to UV - B and UV - C (which are more harmful due to higher energy), UV - A is the least energetic and thus least harmful among valid options.

Answer:

UV - A