Explain the dual theory of light

Our experimental laboratory equipment is big so that human beings can operate it and handle it and fix it. So our experimental laboratory equipment can be built to detect particles or it can be built to detect waves. When you use it to examine tiny tiny stuff, like light rays for example, interesting things happen. If you build an experiment to detect waves and shine light into it the light acts like waves. If you build the experiment to detect particles and shine light into it then the light acts like particles. Whichever you look for, the light behaves that way.

The light behaves as both a wave and a particle. That is the dual theory of light