The optimum wavelength range for sunscreen agents to be effective in protecting the skin from UV radiation is between 290 and 400 nanometers nm . This range covers both UVA 320-400 nm and UVB 290-320 nm radiation, which are the primary types of ultraviolet radiation that cause skin damage and increase the risk of skin cancer. Sunscreen agents should provide broad-spectrum protection, meaning they should effectively block both UVA and UVB rays within this wavelength range.