Final answer:
The region of the electromagnetic spectrum just below the visible light region is the infrared region (b). This type of radiation has lower frequencies and longer wavelengths than visible light. Ultraviolet radiation has higher frequencies than visible light and is more energetic.
Step-by-step explanation:
The region of the electromagnetic spectrum with frequencies just less than those in the visible region is the infrared region. Compared to visible light, infrared radiation has lower energy and longer wavelengths. It is situated between the microwave and visible portions of the electromagnetic spectrum. In terms of energy provided per photon, the correct order from least to most is radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma.
Ultraviolet radiation (UV) has higher frequencies and more energy than visible light, with wavelengths ranging from about 400 nm down to 10 nm. UV radiation can be effective in applications like solar sails due to its higher photon energy compared to visible and infrared light.