Kinetic Energy 1.23 c


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004253593
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Joined: Fri Sep 20, 2013 3:00 am

Kinetic Energy 1.23 c

Postby 004253593 » Sat Oct 12, 2013 3:10 pm

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?

Robert
Posts: 144
Joined: Fri Sep 20, 2013 3:00 am

Re: Kinetic Energy 1.23 c

Postby Robert » Sat Oct 12, 2013 3:20 pm

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.

004253593
Posts: 218
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Re: Kinetic Energy 1.23 c

Postby 004253593 » Sun Oct 13, 2013 3:44 pm

how do you know what objects have rest mass?

powerberry
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Joined: Fri Sep 20, 2013 3:00 am

Re: Kinetic Energy 1.23 c

Postby powerberry » Sun Oct 13, 2013 10:42 pm

The rest mass is the mass of a stationary object. In this case, photons do NOT have rest mass, while electrons do.

704628249
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Joined: Fri Sep 25, 2015 3:00 am

Re: Kinetic Energy 1.23 c

Postby 704628249 » Wed Dec 02, 2015 6:35 pm

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.

Alondra Loera 1A
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Re: Kinetic Energy 1.23 c

Postby Alondra Loera 1A » Thu Dec 03, 2015 10:49 pm

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 .


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