Which require higher bandwidth FM or AM and why?

Frequency Modulation (FM) requires higher bandwidth than Amplitude Modulation (AM) due to the nature of how each modulation method encodes information. FM varies the frequency of the carrier wave to transmit information, which results in a wider range of frequencies being occupied. In contrast, AM varies the amplitude of the carrier wave, which occupies a narrower bandwidth. As a result, FM typically requires about 10 times more bandwidth than AM to accommodate the greater frequency deviations used in the modulation process.