The correct option is (c) 1 and 3 only.
Explanation
The comparison between incandescent bulbs, Compact Fluorescent Lamps (CFLs), and Light Emitting Diodes (LEDs) rests on the principles of energy conversion efficiency and the mechanism of light production (thermal radiation vs. fluorescence vs. electroluminescence).
Statement 1 is Correct.
Incandescent bulbs operate on the principle of the heating effect of electric current (Joule heating). A tungsten filament is heated to extremely high temperatures until it glows. In this process, a vast majority of the electrical energy (approximately 90-95%) is dissipated as heat (infrared radiation) rather than visible light, making them highly inefficient.
Statement 2 is Incorrect.
While CFLs and LEDs are significantly more energy-efficient than incandescent bulbs, they are not 100% efficient.
- CFLs: Operate by passing electricity through a gas to produce ultraviolet light, which excites a phosphor coating. This process generates some heat.
- LEDs: Operate via electroluminescence in a semiconductor. While they run much cooler than filaments, the conversion is not perfect, and the internal driver electronics as well as the diode itself generate heat.
Statement 3 is Correct.
LED bulbs have a much higher luminous efficacy (lumens per watt) compared to incandescent bulbs. This means they require significantly less electrical power to produce the same intensity of light (luminous flux), leading to energy savings.
Key Takeaway:
Incandescent bulbs are inefficient because they rely on heating a filament to emit light. LEDs and CFLs are preferred for their high energy efficiency and longevity, but no artificial light source is perfectly efficient; all generate some amount of heat.