Question

5). Estimate the number of photons emitted in one second from a LED lamp of 10 Watts, if the band-gap energy of the LED is 1.5 eV and 100% energy conversion from electricity to light energy 1 eV = 1.6 x 10-19 Joule. Planck constant h=6.63 x 10-34 Js. Speed of light = 2.998 x 108 msł.

Answer 1

Answere LED lamp =10 Watts = 10JS- Given: Power of • In 1 seconds it provides 105 of energy. Bound gap energy of LED = 105 ev. needed by . 1-sen is photon to get emitted. To find: Number =n=? emitted photon - i) Total of photons emitted in one second Number of photons (per second) - Total energy provided Energy needed by each provided each second = 105 by photon = 1.sen = 1.5x1.6 X10-19 J Elev=/• 6 X10-19 195) 22.4 x 10-19 J Number of photons emitted per second = 10 J/S 2.4x10-19 J energy needed each occus, = 4.17% 1019 photons, Since 100% energy conversion from electricity to light energy hence number of photons. otons emitted per second j.e., n =4.17 X10'a photons