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Chapter 10: Q64E (page 470)

Question: The photons emitted by an LED arise from the energy given up in electron-hole recombinations across the energy gap. How large should the energy gap be to give photons at the red end of the visible spectrum (700nm) ?

Short Answer

Expert verified

Answer

The energy gap to give photons at the red end of the visible spectrum is 1.8 eV .

Step by step solution

01

Given data 

Wavelength of emitted photons, 位=700nm.

02

Concept of photon energy 

Energy corresponding to wavelength of photon is,E=hc位 .

Where, h is Planck's constant =6.64脳10-34J路s.

C Is velocity of light=3脳108m/s .

03

Step 3:Determine the energy gap to give photons at the red end of the visible spectrum

Substitute numerical values in photon energy equation.

E=6.64脳10-34J路s脳3脳108m/s700脳10-9m=0.0284脳10-17J=1.8eV

The energy gap to give photons at the red end of the visible spectrum is 1.8eV

.

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