Different materials are easier to absorb the energy of waves which frequency is in specific range.
Our foods are usually easy to absorb the energy carried by the microwaves. But the plastic or glass is not easy to absorb the energy carried by microwaves. So, the plastic or glass will not be heated greatly in microwave oven. Then the force is pressure times the area of the sail, . The diagonal distance from the point of transmission to a point located directly above the midway point between transmitter and receiver is .