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. (b) Would appropriately sized CdS quantum dots be able to emit blue light?

Video transcript

Hi everyone. So as consider a large crystal of zinc selenium that's illuminated with ultraviolet light. Were asked with appropriately sized zinc selenium quantum dots able to admit yellow light. Considering that it has a band gap of 2.58 electron volts We need to first have like the wavelength of light that corresponds to 2.58 electron volts. For the wavelength is equal to Planck's constant times the speed of light energy. We know that one electron volt was 1.602. I'm Centenary of 19 jewels. And wavelength is what we're looking for. Thanks, constant is 6.626 times 10- Joel's time seconds. The speed of light 3.0 times 10 - eight m/s. And the energy We have 2.58 electron volts. And in one electron volt we have 1.602 pm sent in back of jewels. So you get 4.133. I'm sent in a of 19 jewels. So now if we plug in the values for the wavelength You get 6.626, I'm sente mega 34 jewels time seconds, Times three times 10 to the eight m/s. About 4.133 Thomson to meg of jaws Get 4.81. I'm sensing Ego seven m. And now we need to convert two nm 4. Thomson to negative seven m. And in one m have one time since the ninth nanometers. So you get 481 nanometers and this wavelength corresponds to blue. On the visible spectrum. The band gap of the larger zinc crystal represents the minimum energy in the maximum wavelength of light that can be emitted by this material. So then it's gonna be no. The wavelength of yellow light is greater than the wavelength a blue light. Thanks for watching my video, and I hope it was helpful.