Which one of the following does not convert electrical energy into light energy?
A candle
A light-emitting diode
A laser
A television set
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC CDS-2 – 2018
A) A candle: A candle produces light through the process of combustion, where chemical energy stored in the wax is converted into heat and light energy. It does not use electrical energy.
B) A light-emitting diode (LED): LEDs are semiconductor devices that convert electrical energy directly into light through electroluminescence.
C) A laser: Lasers produce light through stimulated emission. Many types of lasers, particularly semiconductor lasers, are powered by electrical energy. Other lasers may be powered by optical energy, but the principle is often related to electrical excitation or pumping.
D) A television set: A television set’s display screen (whether CRT, LCD, LED, or Plasma) converts electrical energy into light to form images.
Therefore, a candle is the only option that does not convert electrical energy into light energy.
– Electrical energy to light energy conversion is the key process to look for.
– Understand the working principle of each listed item.