What type of electromagnetic radiation is commonly used in the hand held remote control unit of a television set?

Introduction / Context:
Television and other consumer appliances are often controlled from a distance using small hand held remote controls. These devices send signals wirelessly to the television, but the form of electromagnetic radiation used is not always obvious to users because the beam is invisible. This question tests your knowledge of which part of the electromagnetic spectrum is used in typical television remote controls.

Given Data / Assumptions:

• We are dealing with common household television remote control units.
• The remote must transmit commands wirelessly over a short distance.
• The radiation is usually invisible to the human eye.
• Available choices are ultraviolet, visible light, infrared, and none of the above.

Concept / Approach:
Most television remotes use infrared light emitting diodes to send coded pulses to a receiver on the television. Infrared radiation lies just beyond the red end of the visible spectrum and is not visible to the human eye, but can be detected by suitable sensors. It is safe at the low power levels used and works reliably over the short distances found in living rooms. Ultraviolet radiation can be harmful at higher intensities, visible light would be distracting, and radio waves are more common in other wireless devices like Wi Fi and some advanced remotes.

Step-by-Step Solution:
Step 1: Recall that when you press a button on a remote, a small light emitting diode at the front of the remote flashes, though you may not see it with your eyes. Step 2: The invisible flashes are in the infrared region of the spectrum and are detected by a sensor on the television. Step 3: Ultraviolet radiation is higher in energy than visible light and is not commonly used for simple remote control links due to safety and design considerations. Step 4: Visible light could also carry information, but bright flashing lights from every key press would be inconvenient and easily disturbed by room lighting. Step 5: Therefore, the best match from the options for the radiation used in TV remotes is infrared radiation.

Verification / Alternative check:
If you point a television remote at a digital camera or smartphone camera and press a button, you can often see a faint blinking spot on the camera screen, because many digital sensors are sensitive to near infrared radiation. This simple experiment confirms that the remote is emitting infrared, not visible light. Technical specifications and diagrams in service manuals also describe remote control receivers as infrared sensor modules tuned to specific infrared wavelengths and modulation frequencies.

Why Other Options Are Wrong:
Ultraviolet radiation: Rarely used in consumer remotes because it can be harmful and is not needed for short range signalling. Visible light: Would be noticeable and distracting to users, and room lighting could interfere with the signal. None of the above: Incorrect, since infrared radiation is indeed the standard technology used.

Common Pitfalls:
Some learners might assume that because radio waves are widely used in wireless systems, TV remotes must also use radio frequencies. While some advanced remotes do use radio technologies like Bluetooth, the typical simple remote uses infrared. Another mistake is to pick visible light because of the idea of a flashing lamp. Remember that the beam from a standard TV remote is invisible, which matches the infrared part of the spectrum.

Final Answer:
A television remote control commonly uses infrared radiation to send signals to the television.