Class 12 Physics Mcqs

Q:

Which among the following can be detected by an envelope detector?

A) Low frequency AM waves B) Very low frequency AM waves
C) Envelope detectors cannot detect AM waves D) High frequency AM waves
 
Answer & Explanation Answer: D) High frequency AM waves

Explanation: An envelope detector is used to detect high-frequency amplitude modulated (AM) waves. It takes high-level AM waves as input and then provides an output that can be considered as an envelope of the original signal. An envelope detector may consist of a simple RC circuit.

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Sub Category: Class 12 Physics Mcqs

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Q:

The rectifier produces the output required in a communication system.

A) True B) False
 
Answer & Explanation Answer: A) True

Explanation: Yes, this is a true statement. A rectifier converts alternating current (AC), which periodically reverses its direction, to direct current, which travels only in one direction. In a communication system, the modulated signal coming from the intermediate frequency (IF) stage is passed through the rectifier, located in the detector system, and the rectifier, in turn, produces the output required.

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Q:

Which one of the following is the process of recovering the modulated signal?

A) Amplification B) Detection
C) Attenuation D) Transmission
 
Answer & Explanation Answer: B) Detection

Explanation: Detection is the process of recovering the modulating signal from the modulated carrier wave. The transmitted message gets attenuated in propagating through the channel. The receiving antenna is, therefore, to be followed by an amplifier and a detector. The detected signal may not be strong enough to be made use of and hence is required to be amplified.

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9
Q:

Which of the following is not part of the detector system?

A) Rectifier B) Envelope detector
C) Amplifier D) AM wave
 
Answer & Explanation Answer: C) Amplifier

Explanation: The amplifier is a part of the receiver system, of which, the detector is a part of. But, the detector system alone consists of the rectifier, envelope detector, and obviously the amplitude-modulated wave that passes through it.

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Sub Category: Class 12 Physics Mcqs

9
Q:

What is the full form of IF?

A) Intermediate frequency B) Internal frequency
C) Interval frequency D) Immediate frequency
 
Answer & Explanation Answer: A) Intermediate frequency

Explanation: Intermediate frequency (IF) is a frequency to which a carrier wave is shifted as an intermediate step during the transmission of a signal in order to facilitate further processing. In this, the carrier frequency is usually changed to a lower frequency preceding the detection.

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Sub Category: Class 12 Physics Mcqs

11
Q:

Which of the following is false?

A) Bandpass filters filter out the unwanted frequencies B) The transmitting antenna transmits the signal over large distances
C) Attenuation should be reduced for a signal D) The modulated signal is quite strong
 
Answer & Explanation Answer: D) The modulated signal is quite strong

Explanation: No, the modulated signal is quite weak and cannot sustain attenuation over a large distance. So, the modulator is followed by a power amplifier that provides the necessary power, and then the modulated signal is fed to an antenna of appropriate size for radiation.

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8
Q:

A bandpass filter rejects direct current.

A) True B) False
 
Answer & Explanation Answer: A) True

Explanation: Not available for this question

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Category: School MCQs
Sub Category: Class 12 Physics Mcqs

9
Q:

Identify the one that is not required in the process of production of amplitude modulated wave?

A) Square law device B) Rectifier
C) Bandpass filter D) Combination of message and carrier signal
 
Answer & Explanation Answer: B) Rectifier

Explanation: Rectifier is not involved in the process of production of the amplitude-modulated wave. When the message signal is superimposed with the carrier signal to form the desired signal, that signal is in one phase only. So, to overcome this problem we use a square-law device placed in the circuit to square the waveform generated. Bandpass filters are also used in the process.

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