1) Light has both particle and wave properties. It can behave as particles called photons, with energy determined by Planck's constant and wavelength or frequency. 2) The electromagnetic spectrum ranges from gamma rays to radio waves, ordered by decreasing wavelength and increasing energy. 3) Different regions of the EM spectrum, such as visible light, x-rays, and infrared waves, have distinct applications including vision, medical imaging, heating food, and more due to their energy levels and ability to penetrate or be absorbed by matter.