Question

In amplitude modulation, if a message signal of 5 kHz is modulated by a carrier wave of frequency 900 kHz, then the frequencies of the side bands are

• A. 905 kHz, 895 kHz
• B. 900 kHz, 800 kHz
• C. 800 kHz, 700 kHz
• D. 1000 kHz, 900 kHz

Hint:

In amplitude modulation (AM), always remember the sidebands are located at the carrier frequency plus and minus the message frequency.

Answer 1

The Correct Option is A

Step 1: Identify the given values
Message signal frequency \( f_m = 5 \text{ kHz} \)
Carrier frequency \( f_c = 900 \text{ kHz} \) Step 2: Apply amplitude modulation sideband formula
In AM, the sidebands are: \[ f_c + f_m = 900 + 5 = 905 \text{ kHz (Upper Side Band)} \] \[ f_c - f_m = 900 - 5 = 895 \text{ kHz (Lower Side Band)} \] Step 3: State the sideband frequencies
The two sideband frequencies are \( \boxed{905 \text{ kHz and } 895 \text{ kHz}} \)