CdS has a band gap of 2.4 eV. If large crystals of CdS are illuminated with ultraviolet light, they emit light equal to the band gap energy. (c) What about red light?

Video transcript

Hi everyone. So as consider a large crystal of sing silent night that's illuminated with ultraviolet light. Who asked what appropriately sized sink cell and I quantum dots be able to admit green light. Considering that it has a band gap of 2.58 electron volts, We need to first calculate the wavelength of light that corresponds to 2.58 electron volts. We're gonna use the equation wavelength the plane's constant times the speed of light by by the energy. We know that one electron volt Because 1. I'm sensing negative 19 jaws. So the wavelength is what we're looking for. Thanks, constant is 6.626 times 10 10 9 joe's time seconds of light, 3.0 times 10 to the eight penis per second and their energy It's 2.58 electron volt. We need to convert to jewels. So one electron volt was 1.602 am sentiment of 19 jewels. And we get 4.133 Thompson to make up 19 jewels. So now if you plug in the values into the equation for the wavelength We get 6.6 to 6 times since the jules, I'm seconds Times three times 10-8 m/s, About about 4.133. I'm santa mega 19 jewels. They get 4.8, 1 sentence of seven m. So now I need to convert this two nanometers, 4.8, 1 times 10 to the -7 m. And in one m We have one times 10 to the nine nm. So you get 481 nanometers, so this wavelength corresponds to blue on the visible spectrum. The band gap of the largest zinc selling my crystal represents the minimum energy, the maximum wavelength of light that can be admitted by the material. So the answer is no. The weight of the green light is greater than a wavelength other blue light. Thanks for watching my video, and I hope it was helpful.