Semiconductor Electronics Part 1

Given, energy gap of LED, E=1.9eV
Speed of light in free space, C=3×108ms−1
Planck's constant, h=6.63×10−34J−s
As we know that, E=‌

hc

λ

⇒‌‌λ=‌

hc

E

⇒‌‌λ‌‌=‌

6.63×10−34×3×108

19×1.6×10−19

‌‌=654×10−9m
‌‌=654nm
As, wavelength of red light is 600nm.
∴ Required wavelength will be of red colour.