Previous Year Question

Traditional Remote Controls for Television Receivers use Infrared Radiation (IR). It is an invisible part of the Electromagnetic Spectrum, with wavelengths longer than those of red visible light.

The wavelength of Infrared Radiation generally ranges from approximately 700 nanometres (nm) to 1 millimetre (mm). Television remotes commonly use Near-Infrared Radiation with a wavelength of approximately 940 nm.

Working Mechanism of a Remote Control: An Infrared Light Emitting Diode (IR LED) in the remote emits pulses of infrared light when a button is pressed. These pulses are transmitted as specific digital codes. The IR Receiver in the television detects these signals and converts them into electrical signals, allowing the television to change channels, control volume, and execute other commands.

Most traditional IR remotes modulate infrared signals at a Carrier Frequency of approximately 38 kHz. This helps the receiver distinguish signals from the remote from other infrared radiation present in the surroundings.

Infrared Radiation has a longer wavelength and lower frequency than Visible Light, whereas Ultraviolet Radiation has a shorter wavelength and higher frequency than Visible Light. Therefore, traditional television remotes use Infrared Radiation rather than ultraviolet or visible light.

Infrared remote operation generally requires a suitable signal path between the remote and the television receiver. Although walls and other opaque obstacles can block the signals, reflection from certain surfaces may allow the remote to function even without being pointed directly at the television. Some modern Smart TV remotes also use Bluetooth or Radio Frequency (RF).