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Kinetic Energy 1.23 c

Posted: Sat Oct 12, 2013 3:10 pm
by 004253593
1.23 c. What is the wavelength of the radiation that cause photejection of the electron? I am confused why you use KE to find this out? How do you know when to use KE equation?

Re: Kinetic Energy 1.23 c

Posted: Sat Oct 12, 2013 3:20 pm
by Robert
You would use the kinetic energy formula 1/2 mv^2 because that applies to objects with rest mass. So when you have that energy, add it to the threshold (work function) energy (part b) and then solve for wavelength.

Re: Kinetic Energy 1.23 c

Posted: Sun Oct 13, 2013 3:44 pm
by 004253593
how do you know what objects have rest mass?

Re: Kinetic Energy 1.23 c

Posted: Sun Oct 13, 2013 10:42 pm
by powerberry
The rest mass is the mass of a stationary object. In this case, photons do NOT have rest mass, while electrons do.

Re: Kinetic Energy 1.23 c

Posted: Wed Dec 02, 2015 6:35 pm
by 704628249
Well, Energy or hv= Work needed to remove an electron + the Kinetic Energy. So you plug in the given information and find out what you need.

Re: Kinetic Energy 1.23 c

Posted: Thu Dec 03, 2015 10:49 pm
by Alondra Loera 1A
Just to clarify photons are wave particles and according to special relativity, light is constantly traveling with speed c. Therefore photons are never at rest and do not have a rest mass but because they have energy they do have a mass. Particles such as electrons and protons do have a rest mass .