# +2 Physics - Communication Systems - Part 4

Questions from 26-35 are provided in this blog post. We will aim to cover as may important questions as possible, which would help the candidates to prepare well from an examination perspective.

26) Look at the diagram below and identify the blocks numbered (1) and (2) in a Superheterodyne AM receiver.

a) Mixer and FM amplifier
b) Detector and Mixer
c) Detector and Oscillator
d) Mixer and Detector

27) A ------------- is a device that prevents a signal voltage from exceeding a certain peak value.

a) Oscillator
b) Mixer
c) Limiter
d) Amplifier

28) In a television system, usually, sound signals are ------------- while picture signals are ------------

a) Frequency modulated, Amplitude Modulated
b) Amplitude Modulated, Amplitude Modulated
c) Frequency Modulated, Frequency Modulated
d) Amplitude Modulated, Frequency Modulated

29) Vidicon television camera converts ----------

a) electrical energy to light energy
b) electrical energy to magnetic energy
c) light energy to electrical energy
d) magnetic energy to electrical energy

30) ------- is a principle where the resistance of target material decreases when exposed to light.

a) Photo elastic effect
b) Photonics
c) Photo Conductivity
d) Electrostatics

31) In India, frame repetition rate has been standardized at ---------- frames per second.

a) 25
b) 15
c) 30
d) 40

32) A ------------ is used to convert digital signals to analog signals capable of being transmitted over telephone lines.

a) Modulator
b) De-modulator
c) Modem
d) Television

33) The man made Satellite Sputnik, was launched in

a) 1947
b) 1957
c) 1953
d) 1943

34) In amplitude modulation, the band width is

(a) equal to the signal frequency
(b) twice the signal frequency
(c) thrice the signal frequency
(d) four times the signal frequency

35) In phase modulation

(a) only the phase of the carrier wave varies
(b) only the frequency of the carrier wave varies.
(c) both the phase and the frequency of the carrier wave varies.
(d) there is no change in the frequency and phase of the carrier wave