Below is a text with blanks. Click on each blank, a list of choices will appear. Select the appropriate answer choice for each blank.
Light is usually described as a form of energy and it is indeed a kind of electromagnetic energy, not much different from radio waves, television signals, heat, and X-rays. All of these are made up of waves that spread, bend, interfere with one another, and react with obstacles in their path, rather like waves in water. A physicist might tell you that light, along with all its electromagnetic relatives, is really a form of matter, little different from more substantial matter such as houses and, like them, it is made up of individual particles. Light particles, called photons, travel in streams, similar to the way in which water pours through a hose. To most people, this might sound paradoxical or illogical, as many things to do with physics seem to these days. How can light be both energy and matter, wave and particle? The reason it can be is, in fact, not at all complicated : all energy is a form of matter. Almost everybody recognizes- even if they do not understand- Einstein's famous equation, E =mc2, which spells it out: E refers to energy and m to the mass of matter. Furthermore, all matter has some of the characteristics of waves and some of particles, but the waves of such solid-seeming things as houses are not discernable and can generally be ignored because ordinary matter acts as if it were made up of particles.
