This transfer is radiation. This type of heat transfer is composed of electromagnetic waves from the Sun either through infrared or ultraviolet rays. Radioactive heat transfer is the only way to transfer heat from one place to another without a medium.
Light from the Sun passes through the glass roof to heat plants and the ground inside the greenhouse. These objects then emit infrared radiation, which is absorbed in the glass roof. Thermal energy is trapped in the greenhouse, keeping the building warm.
