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Numerade Educator



Problem 23 Medium Difficulty

(II) Barium has a work function of 2.48 eV. What is the maximum kinetic energy of electrons if the metal is illuminated by UV light of wavelength 365 nm?What is their speed?


$0.92 \mathrm{eV}$ $5.7 \times 10^{5} \mathrm{m} / \mathrm{s}$


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Video Transcript

ask for the given problem. Will First Judd town to determine which is couldn't s O work function often bury him, which is generated as w is equal to two point for each electron vote says one electron void is equal to 1.6 into tennis to minus 19 Jews. They're for W busy quick oh, 2.48 into 1.6 into tennis to minus 19 which is coming gas tree for 96 feet into tennis to minus 19 Troop. So we're basically converting from electron were to choose. Also a violent off light is given as Lambda, which is 3 65 9 millimeter. So if we try to convert it into meter, it is going to be 3 65 into tennis. True. Minus nine meters. Now. In this problem, we need to find two quantities. The 1st 1 is Maxima Kinetic energy off in a trance and the 2nd 1 is speed of rituals. Now here we start Formula for four grand energy is denoted as easy quote to each time See over Landa And here EJ is equipped to which is no. This plan is constant. C is equal to speed off light and Lambda is known as virulent by substituting all the values in the formula for E, that is next time. See over Lambda, we put devices right now, which is 6.63 into tennis to minus 30 for that is true. Second multiplied by three include and Rescue eight made a per second, which is valid for C over 3 65 in pretending it's two minus nine meters, which is equivalent. And by calculating this, we get it as 5.449 in good earnest to minus 19 Druids when we consider the kind of big energy here which we need to calculate which is given by the formula e minus w. So here Well, we already have. That is 5.449 into tennis to minus 90 minus w is 3.296 lead, including minister minus 19 which we have already calculated previously. So we're just coming as 1.40 to 1 one point for it one, including minus two minus 19 truths. We can convert this value Kinetic energy music will do what we have court as 1.4 800 initial mine in jewels. Okay, in ju in a triangle. So what we need to do? 1.40 to 1, including Mr minus 19 divided by 1.6 in good and Mr minus 90 which is coming as zero point nine to a strong word as the fighting on here. In order to calculate the answer for B, that is speed off electrons calculate speed off electrons. We need to use a formula for kinetic energy which has given us half into M into the square. But M stands for you're a music culture 9.11 include Ennis to minus 31 kilogram riches. Monster electron kind antic energy value be already called So therefore, in order to comfort value off me, it is going to be a squared off two times kinetic energy over in. But you just tried to conquer this right now. So it is two times the value of kinetic energy is 1.481 include Ennis to minus 90 over myself. Electron is 9.11 in true penitence to minus 30. But so finally therefore we get Risi quitter. 570 drew 08 points year for which we can already does. 5.70 Neto, turn the rest. Five meter per second since its velocity. And this is going to be on, sir.