Question on kinetic energy

Emma Randolph 1J
Posts: 65
Joined: Fri Sep 28, 2018 12:29 am

Question on kinetic energy

For the photoelectric effect equation, is the kinetic energy always equal to 1/2mv^2 or can that be used for any part of the equation like the energy of the photon?

Posts: 77
Joined: Fri Sep 28, 2018 12:28 am
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Re: Question on kinetic energy

That equation is just for the kinetic energy of the ejected electron
You can't use that equation for the energy of a photon because mass is required and a photon has no measurable mass
hope this helped:)

Brian Kwak 1D
Posts: 88
Joined: Fri Sep 28, 2018 12:17 am

Re: Question on kinetic energy

Thank you for the clarification.

JiangJC Dis2K
Posts: 72
Joined: Fri Oct 12, 2018 12:16 am

Re: Question on kinetic energy

No. 1/2mv^2 can only be used for particles that have mass and velocity (essentially particles in motion). This cannot be applied to photons because they have no rest mass. Therefore, the equation hc/E is used instead of h/p.

Mikka Hoffman 1C
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Joined: Fri Sep 28, 2018 12:23 am
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Re: Question on kinetic energy

Kinetic energy of the ejected photon is given by 1/2mv^2 and the energy of the photon is given by the equation E=hv

Sydney Stump
Posts: 30
Joined: Fri Sep 28, 2018 12:17 am

Re: Question on kinetic energy

It is true that Ek is always equal to 1/2mv^2 - but it can also be used to find the energy of a photon in the sense that Ephoton = Ekinetic + Threshold Energy.