In this position it receives and focuses reflected pulses. The radar pulses sent out by the antenna travel through the air at a speed of 186,000 miles a second until they strike a solid. Upon striking an object, a portion of the energy of the pulses is reflected back to the antenna in the form of waves. All objects do not reflect these microwaves equally well. The strength of the reflection depends upon the size, shape, and composition of the object.
Metal objects are the best reflectors of microwaves.
Wood and plastic produce weaker reflections than does metal. The reflected microwaves form a pattern which is an image of the object that was struck by the transmitted waves. When reflected pulses return to the antenna, they are directed to the receiver. In the receiver their voltage is amplified by a multiple of several million. This alternating voltage is then converted to direct current and impressed upon a cathoderay oscilloscope.