JEE Main · 2019 · 09 Apr 2019 · Shift 2 · Semiconductors

An antenna radiates and picks up electromagnetic waves efficiently only when its physical length is comparable to the wavelength it is handling. The wave that actually travels through space is the carrier, whose wavelength is $\lambda =\frac{c}{f_c}$, so the antenna size is tied to the carrier wavelength and hence to $\frac{1}{f_c}$. A higher carrier frequency means a shorter wavelength and a physically smaller antenna, so both the transmitting and receiving antennas scale inversely with the carrier frequency. The modulation (signal) frequency plays no part here, because it is the carrier that is launched into space.