For good demodulation of AM signal of the carrier frequency f­_c, the value of RC is

CONCEPT:

• Demodulation: The process of recovering the audio signal from the modulated wave is known as demodulation or detection.
• It is the reverse of modulation.

EXPLANATION:

• The input circuit is a parallel combination of inductance Land variable capacitor C. It is called a tuned circuit.
• By adjusting the frequency of this circuit, the desired modulated radio signal is resonantly selected from the different signals picked up by the antenna. The diode rectifies this signal.
• For exact recovery of the original message, the following condition must be satisfied:

           \(\frac{1}{{{f_c}}} < RC < \frac{1}{{{f_m}}}\)

• Therefore option 3 is correct.