LED's have following advantages over incandescent low power lamps.
A. Low operational voltage and less power.
B. No warm up time required.
C. LED must at least have a band gap of 1.8 eV .
D.\(GaAs _{1-x} P _x\) is used for making LED's of different colours.
E. The band width of emitted light in LED's is 100 Å to 500Å .
Choose the correct answer from the options given below:

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.