Communication system Physics 12 Grade

Consider the LC circuit at right. At the time shown the current has its maximum value. At this time

• The charge on the capacitor has its maximum value

• The magnetic field is zero

• The electric field has its maximum value

• The charge on the capacitor is zero

A microwave has a frequency of f₁. A gamma ray has a frequency of f₂. Which one has a greater speed?

• The microwave

• They have the same speed

• The gamma ray

• We need to know the wavelengths to be able to solve

Which of the following lists of electromagnetic waves is in order of increasing wavelength?

• gamma rays, X-rays, radio waves, ultraviolet

• microwaves, light, ultraviolet, gamma rays

• ultraviolet, light, microwaves, radio waves

• X-rays, gamma rays, infrared, light

Amplitude modulation is

• Change in amplitude of the carrier according to modulating signal

• Change in frequency of the carrier according to modulating signal

• Change in amplitude of the modulating signal according to carrier signal

• Change in amplitude of the carrier according to modulating signal frequency

The graph shows the frequency spectrum of an AM radio wave carrying an audio signal of a single frequency. Determine the frequency of the audio signal.

• 1kHz

• 3 kHz

• 5 kHz

• 7 kHz

An analogue signal is sampled at a frequency of 5.0 kHz. Each sample is converted into a four-bit number and transmitted as a digital signal. Show in which number equal to code 0110.

• 2

• 4

• 6

• 8

The Y-input terminals of a cathode-ray oscilloscope (c.r.o.) are connected to a supply of amplitude 5.0V and frequency 50Hz. The time-base is set at 10ms per division and the Y- gain at 5.0V per division.

Which trace is obtained?

• 
• 
• 
• 

A burst is a brief flash or pulse of light or other electromagnetic wave. Gamma- ray bursters are objects in the universe that emit pulses of gamma rays with high

energies. The frequency of the most energetic bursts has been measured at around 3∙ 10²¹ Hz. What is the wavelength of these gamma rays?

• 1∙ 10^-13

• 2∙ 10 ^-13

• 3∙ 10 ^-13

• 4∙ 10 ^-13

Which of the following emits infrared radiations?

• Hot iron

• Ice

• Freezing mixture

• Wet cloth

Cross talk between fiber optic cables

• Doesn’t exist

• Minimal effect

• Moderate effect

• High effect