Diffraction is a term that describes the phenomenon of waves being able to bend around obstacles, or to pass and spread through small openings. The phenomenon was first observed, recorded, and demonstrated by Italian scientist Francesco Maria Grimaldi in 1665. A waves ability to diffract, or bend, is directly related to its wavelength and frequency. The wavelength is how long the wave is from one crest to another, or one trough to another. The frequency is how many waves pass per second. The lower energy waves, such as radio waves, are longer and possess a higher ability to refract. This is why you can hear a cars stereo system with bass frequencies pumping long before you can actually see the car. The higher energy waves have shorter wavelengths and are not as able to refract as their lower energy relatives. So, the lower the energy, the more a wave will be able to refract, or bend, around obstacles and through openings.