Microwaves are detected by which of the following?

Microwaves are detected using an aerial and receiver, which are designed to capture the specific frequency and wavelength of microwave radiation. An aerial, often referred to as an antenna, can convert microwave signals into electrical signals. The receiver then processes these electrical signals to interpret the information carried by the microwaves. This method is widely used in communication technologies, such as radar and satellite transmission, where the efficiency of capturing and converting microwave signals is crucial.

In contrast, photovoltaic cells primarily detect visible light and convert it into electricity, making them unsuitable for microwave detection. Thermal sensors measure temperature changes and might respond to microwaves indirectly through heat, but they are not specialized for detecting microwave signals directly. Piezoelectric devices generate an electric charge in response to applied mechanical stress; they are not typically used for detecting electromagnetic waves like microwaves. Thus, the combination of an aerial and receiver is the most effective and appropriate method for detecting microwaves.