The news often speak about the greenhouse phenomenon and the global warming.
    In greenhouses the roof and sides are made of transparent or translucent material (glass, plastic etc). The electromagnetic radiation (light) enters (goes into) the usually glass building, where it hits the ground and diffused. This means that the wavelength changes. (Think of a "crazy" ball which hits the ground bounces and then goes to a different direction to the one it came from). Because of this wavelength change, the electromagnetic radiation can not pass through the glass and leave; therefore it is "trapped" inside the greenhouse. In terms of energy, this electromagnetic radiation collides with the molecules of whatever exists inside the green house (plants, air etc); and increases the kinetic energy of it.

    In the global greenhouse the role of the glass sides and roof play the clouds of pollutants that are gathered on the atmosphere.