The universe is filled with energy that can take on different forms. For instance, matter is energy. There may be two distinct types of matter in the universe: ordinary matter and dark matter. Ordinary matter can form structures like gas clouds, moons, planets, stars, and galaxies. Dark matter does not interact with radiation but exerts a significant gravitational force in the universe. Radiation is also energy. Light is electromagnetic radiation emitted by hot bodies. Light is characterized by its frequency or wavelength. For instance, the cosmic background radiationCosmic Microwave Background Radiation (CMBR) is microwave radiation. Solar radiation covers a range of frequencies, from radio waves to gamma rays, including visible light that illuminates Earth. The composition of frequencies in a wave is called “spectrum”.