54738.A T.V. tower has a height 150 m. What is the population density around the T.V. tower if the total population covered is 50 lakh? The radius of earth is $6.4×10^6m$.
800$km^{−2}$
829$km^{−2}$
82.6$km^{−2}$
826.6$km^{−2}$
54739.The sky wave propagation is suitable for radio- waves of frequency
upto 2MHz
from 2MHz to 20MHz
from 2MHz to 30MHz
from 2MHz to 50MHz
54740.The maximum range $d_max$, of radar is
proportional to the cube root of the peak transmitted power
proportional to the fourth root of the peak transmitted power
proportional to the square root of the peak transmitted power
Not related to the peak transmitted power at all
54741.The maximum range dmax, of radar is
proportional to the cube root of the peak transmitted power
proportional to the fourth root of the peak transmitted power
proportional to the square root of the peak transmitted power
Not related to the peak transmitted power at all
54742.Audio signal cannot be transmitted because
the signal has more noise f Thinking
the signal cannot be amplified for distance communication
the transmitting antenna length is very small to design
the transmitting antenna length is very large and impracticable
54743.An antenna is a device
that converts electromagnetic energy into radio frequency signal
that converts radio frequency signal into electromagnetic energy
that converts guided electromagnetic waves into free space electromagnetic waves and vice-versa
None of these
54744.A laser beam is used for carrying out surgery because it
is highly monochromatic
is highly coherent
is highly directional
can be sharply focused
54745.Which of the following frequencies will be suitable for beyond-the horizon communication using sky waves?
10 kHz
10 MHz
1 GHz
1000 GHz
54746.Modulation is the process of superposing
low frequency audio signal on high frequency waves
low frequency radio signal on low frequency audio waves
high frequency audio signal on low frequency radio waves
low frequency audio signal on low frequency radio waves
54747.Which mode of communication is not employed for the transmission of T.V. signals?
Ground wave propagation
sky wave propagation
space wave propagation
None of these
54750.Elements which have properties of metals and nonmetals are
amorphous
crystalline
metalloids
metals
54751.Which of the following methods is not used for the prevention of corrosion?
greasing
painting
plating
Heating
54754.Galvanization is a method to
protect iron metal from corrosion
extract iron from its ore
protect food from rancidity
improve the ductility property of the metal
54755.Rusting of iron could take place in
distilled water
ordinary water
distilled and ordinary water
none of the above
54756.Voltaic cells generate electricity by
spontaneous redox reaction
non spontaneous redox reaction
sublimation reaction
thermochemical reaction
54757.Widening of a river valley takes place due to
corrosion
lateral erosion
corrasion
hydraulic action