Kinetic Energy 1.23 c

[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?

[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.

[004253593]

how do you know what objects have rest mass?

[powerberry]

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

[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.

[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 .