A minimum energy of 7.21⨉10^-19 J is required to produce the photoelectric effect in chromium metal. (b) Light with a wavelength of 2.50⨉10^-7 m falls on a piece of chromium in an evacuated glass tube. What is the minimum de Broglie wavelength of the emitted electrons? (Note that the energy of the incident light must be conserved; that is, the photon's energy must equal the sum of the energy needed to eject the electron plus the kinetic energy of the electron.)

Video transcript

Hey everyone welcome back. So let's get started with this video. So here they want us to calculate, They broke a wavelength of an electron moving at a speed of 4.0 times 10 to the 5m/s. So recall that the wavelength equation is wavelength is equal to Planck's constant over mass terms of the Lost City. Okay, So then Plank's constant H. That is equal 6.6-6 times 10 To the negative kilograms times meters squared over second. Okay, Mass here we're dealing with an electron And the mass of an electron that is nine 0. times 10 To the negative kilograms. And then finally the other value we need is velocity and were given velocity. We're told that it's moving at a speed of four zero times 10 to the five meters per second. So then we have everything we need to plug in. So then let's go ahead and plug in values. So then wavelength is equal to six 6, 26 times 10 To the negative grams. This is kilograms. There we go. Times meters squared over second Over mass, which is 9.11 times 10 to the - telegram. This is a mass of an electron Times Velocity 4. times 10 to the five meters per second. So then kilograms, cancel out. Better cancel out 2nd, cancel out and we get a wavelength of 1.8, 1 Times 10 to the - meters. Okay? But if you see our answer choices are given in nanometers and we sell for meters. So then let's go ahead and convert two nanometers. So then one meter was equal to 10 to the nine nanometers. So then the meters cancel out. And we get 1. nanometers. We look at our answer choices and that's going to be a Okay. Thank you for watching. I hope this helps and I'll see you in the next video.