Question

The colour of light emitted by LED depends on:
(a) Its reverse bias
(b) The amount of forward current
(c) Its forward bias
(d) Type of semiconductor material

Answer 1

Hint: We will check all the options that satisfy these 2 conditions for the correct solution.
The colour of the light emitted by the LED depends on the wavelength of the light which in turn depends on the semiconductor material used in the diode while manufacturing LED.
No other factor is responsible for the colour of light.

Complete step by step solution
We will analyse all the options one by one.
Option(a) says that the colour of light emitted by LED depends on its reverse bias. But LED will not glow in reverse bias. Biasing in LED is like switching it on or off. LED is on when it is forward biased and off when it is reverse biased.
Hence, option(a) is wrong.
Option(b) says that the colour of light emitted by LED depends on the amount of forward current. Increasing the current will increase the intensity of the light but will have no effect on the colour of the light emitted.
Hence, option(b) is wrong.
Option(c) says that the colour of light emitted by LED depends on its forward bias. Biasing in LEDs has no relation with the colour of light emitted.
Hence, option(c) is wrong.
Option(d) says that the colour of light emitted by LED depends on the type of semiconductor material. The colour of the light emitted by LED is determined by the wavelength of the light emitted, which in turn is determined by the semiconductor compound used in forming the \[P - N\] junction during manufacturing.

Hence, option(d) is the correct solution.

Additional Information
The intensity of the light emitted by the LED is directly proportional to the second power of the current flowing through it.

Note
Majority of students go wrong in this question with option(b). Always remember that the current flowing through the LED has nothing to do with the colour of the light emitted by it. The colour of the light emitted by the LED is an intrinsic property of the material used to make it.