1). Systems at higher frequencies can carry more information
(data, pictures, channels, etc.) than at lower frequencies.
2). The "dish" antennas used for satellite communication, both on
the ground and on the satellite, have more gain at higher frequencies
than they have at lower ones.
3). Radio waves at frequencies lower than VHF reflect off of the
ionized layers of the atmosphere and return to Earth. They never
get out to where the satellites are.
4). All of the communication spectrum (frequencies) below VHF
were already being used for other services by the time satellite
communication started (in the 1960's).
Answer:
Microwave towers are telecommunications towers that use microwaves to transmit telephone and television signals to other microwave towers.
Explanation:
This technology replaced existing transmission wires, but it is almost entirely obsolete as of 2015 due to the advent of fiber optics and other modern methods of telecommunication.
Answer:
m = 4.5021 kg
Explanation:
given,
Apparent mass of aluminium = 4.5 kg
density of air = 1.29 kg/m³
density of aluminium = 2.7 x 10⁷ kg/m³
true mass of the aluminium = ?
Weight in Vacuum
W = m g
W = ρV g
Air buoyancy acting on aluminium
B = ρ₀V g
Volume is the same in both cases since the volume of the aluminum
displaces an equal amount of volume air.
Apparent weight:
ρV g − ρ₀V g = 4.5 g
ρV − ρ₀V = 4.5

m = ρV


m = 4.5021 kg
Answer:
(C) zero (there is no net horizontal component of the E-field)
Explanation:
If we subdivide the bar into small pieces, each piece (dx) contains a charge (dq), the electric field of each piece is equivalent to the field of a punctual electric charge, and has a direction as shown in the attached figure. For each piece (dx) in the negative axis there is another symmetric piece (dx) in the positive axis, and as we see in the figure for symmetry the sum of their electric fields gives a resultant in the Y axis (because its components in X are cancelled by symmetry).
Then the resultant of the electric field will be only in Y.
(C) zero (there is no net horizontal component of the E-field)
Out of that list, the concave mirror is the only item that can concentrate sunlight and heat into a small area. But if you could get ahold of a convex lens, that would be even better.