Question

The AM range of radio waves has frequency:
(A). Less than 30MHz
(B). More than 30 MHz
(C). Less than 20000Hz
(D). More than 20000Hz

Answer 1

Hint: AM stands for amplitude modulation, which is a process of modulating radio waves with higher frequency waves so that it can be sent to longer distances. This helps to prevent the attenuation of the source signal.

Complete step-by-step answer:
Amplitude modulation is a modulation technique used in electronic communication. In amplitude modulation, the amplitude of the carrier radio wave is varied proportional to the amplitude of the source or message signal. The frequency range of AM waves is from 540 to 1600KHz. So the maximum frequency range is 1.6MHz which is less than 30MHz.
So the answer to the question is option (A)- Less than 30MHz.

Additional Information:
If we want to send a signal through a long distance, there is a chance that the signal will lose its content due to attenuation. In order to protect the signal from attenuation, we superimpose the message signal with a carrier signal which has a higher frequency than the message signal. This process of superimposing the message signal with varying some aspects of the carrier signal is known as modulation of a signal. Demodulation is the process by which the message signal is extracted from the carrier signal at the receiving end.

Note:A disadvantage of all amplitude modulation techniques, not only standard AM, is that the receiver amplifies and detects noise and electromagnetic interference in equal proportion to the signal. AM is also inefficient in power usage; at least two-thirds of the power is concentrated in the carrier signal which is something to avoid.
A demodulator which is used to extract the message signal from the carrier signal consists of a diode which is configured to act as an envelope detector. Another demodulator which can offer better quality is the product detector, which has a slightly complex circuit compared to the basic demodulator.