(i) The intensity of a light pulse travelling along a communication channel decreases exponentially with distance x according to the relation I = I_0 e^(-alphax) , where I_0 is the intensity at x = 0 and alpha is the attenuation constant. Show that the intensity reduces by 75 percent after a distance of (ln 4)/(alpha) (ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation dB = 10log_10 (I//I_0). What is the attenuation in dB//km for an optical fibre in which the intensity falls by 50 percent over a distance of 50 km?
Demodulation is the reverse process of modulation, which is performed in a receiver to recover the original modulating signals. At the receiving end, the signals are generally weak due to attenuation in the channel. The receiver selects only the desired signal, rejecting the unwanted (noise) signals and amplifies the same. Read the above passage and answer the following questions: (i) What are the main functions of a demodulator? (ii) Give any two examples of demodulators. (iii) What does the phenomemom of demodulation imply in day to day life?
InItroduction of attenuated pathogens in human body results in______________.
Suspension of attenuated pathogen that stimulates antibody formation is:
NAVNEET PUBLICATION - MAHARASHTRA BOARD-DEFINITIONS-COMMUNICATION SYSTEMS
