What is the need for doing modulation ?

Options

A. To increase the intensity of audio signal
B. To decrease the intensity of audio signal
C. To transmit audio signal to large distances
D. None of the above

Answer

### Step-by-Step Solution:

1. **Understanding Modulation**: Modulation is the process of varying a carrier signal in order to transmit information. It is essential in communication systems to effectively send signals over long distances.

2. **Challenges of Direct Transmission**: If an audio signal is transmitted without modulation, its intensity decreases as the distance from the transmitter increases. This results in poor quality and loss of information in the received signal.

3. **Purpose of Modulation**: The primary need for modulation is to enable the transmission of audio signals (or any information) over large distances without significant loss of quality. By modulating the signal, it can be transmitted more efficiently.

4. **Options Analysis**:
- The first option suggests that modulation is used to increase the intensity of the audio signal. However, while a demodulator can adjust the intensity at the receiving end, modulation itself does not inherently increase intensity.
- The second option implies that modulation is used to decrease the audio signal intensity. This is also incorrect for the same reason.
- The third option correctly states that the need for modulation is to transmit audio signals over large distances effectively.

5. **Conclusion**: Therefore, the need for modulation is primarily to allow the effective transmission of audio signals over long distances, ensuring that the information reaches the receiver with minimal loss.