Question

Television signals on earth cannot be received at a distance greater than 100 km from the transmission station the reason behind this is that
A. The receiver antenna is unable to detect the signal at a distance greater than 100 km.
B. The TV program consists of both audio and video signals.
C. The TV signals are less powerful than radio signals.
D. The surface of earth is curved like a sphere.

Answer 1

Hint: In this question we are asked the reason for which the television signals on earth cannot be received at a distance greater than 100 km. So, we will first discuss how the television signals are received and what can stop the television signals from being received. We will evaluate these reasons and confirm our answer.

Complete answer:
The television signals are carried by wire to an antenna which is often on a high mountain or building. The TV signals are transmitted as electromagnetic waves or radio waves. The TV transmitter transmits the signal which is then received by the receiver antenna. We know that radio transmits the sound wave. The TV along with sound also transmits the picture which is carried by radio waves as electricity and magnetism. The receiver receives these signals and converts them into picture.
Now, we know that just like the telephone signals, the television signals can’t penetrate the parking garages or concrete construction. Also, the electromagnetic waves when travel through the metals, there is small leakage of the waves. When travelling long distances these signals can be lost completely. Over the air television can also be blocked by tall structures like mountains, trees or skyscrapers. Also, we know that the earth’s surface is spherical and the curve of earth can obstruct the flow of signals after a certain distance. Therefore, even the signals from mountain tops can be obstructed when travelling on earth. The receiver antenna has the capability to receive signals from space. It does not affect the receiving quality if the waves are both audio and video. The electromagnetic waves are as powerful as radio waves. So all the other options are not applicable.

Therefore, the correct answer is option D.

Note:
We know that receiver antennas are strong enough to receive the signals from satellites in space. So travelling a large distance is of no problem for the signals. The waves can transmit both audio and video signals. Basically, the transmitter transmits the picture and the receiver shows them as a slide with the sound waves. These slides are changed at a very high speed that the brain processes it as a video. TV can be called an electronic flip book with audio.