Physics - Semiconductors Question with Solution | TestHub

The brightness of light emitted by an LED is directly proportional to the forward current flowing through it. By varying the forward current or by using techniques like Pulse Width Modulation (PWM), the brightness of an LED can be easily controlled.

Therefore, the statement 'Brightness of light emitted by LED cannot be controlled' is incorrect.

The other statements are correct: LEDs are highly energy-efficient, have a long operational lifetime, and their emitted colours are generally stable and do not fade out.