Week 2,3,4 Homework Question 15

[kaylagonzalez]

I have been trying to solve this problem for a long time but cannot seem to understand it. The question is that an electron beam has a wavelength of 0.0221 nm. What is the kinetic energy K of an electron in the beam, expressed in electron volts? I don't want the answer but if someone can explain how to work through it and the steps that need to be taken I would apricate it. Thank you!

[Katelyn Wu 1I]

Hi! To solve for kinetic energy (K), you can first start off with the equation K=1/2mv^2. Based on this, you will want to figure out what you can plug in based on what was given to you. The mass of an electron is given on the equation sheet (9.109x10^-31 kg) so you can immediately plug that into the equation. However, because you are not given the velocity (v), you will have to rearrange the given information to fit v. Using the equation lambda=h/p, you can replace p with mv to get lambda=h/mv. You will now have all the known values to solve for v, which you can plug into K=1/2mv^2 to reach your answer!