As shown, a large hill lies between a transmitter of radio waves and a receiver, preventing any direct route. The receiver still detects the signal from the transmitter even though the radio waves do not pass through the hill. Which row is right?
- AA possible way: diffraction round the hill; a stronger signal is received using longer wavelengths
- BA possible way: diffraction round the hill; a stronger signal is received using shorter wavelengths
- CA possible way: refraction round the hill; a stronger signal is received using longer wavelengths
- DA possible way: refraction round the hill; a stronger signal is received using shorter wavelengths