Previous Year Question
What type of electromagnetic radiation is used in the remote control of a television?
Infrared
Ultraviolet
Visible
None of the above
Correct Answer: A
Detailed Solution
A conventional TV remote contains an Infrared LED. When a button is pressed, the remote transmits the electrical command to the television in the form of coded infrared light pulses.
An infrared sensor on the television receives these pulses and converts them into an electrical signal. The television then executes the corresponding command such as changing the channel, controlling the volume or switching the power on or off.
Infrared lies in the electromagnetic spectrum at longer wavelengths and lower frequencies than visible red light. It is invisible to the human eye.
Infrared is suitable for TV remotes because it provides simple and effective short-distance, line-of-sight communication. However, if an opaque object blocks the path between the remote and the TV sensor, the signal is generally interrupted because infrared does not readily penetrate solid barriers such as walls.