Question on kinetic energy

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

Question on kinetic energy

Postby Emma Randolph 1J » Fri Nov 02, 2018 4:54 pm

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?

Nada AbouHaiba 1I
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Re: Question on kinetic energy

Postby Nada AbouHaiba 1I » Fri Nov 02, 2018 4:57 pm

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
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Re: Question on kinetic energy

Postby Brian Kwak 1D » Sat Nov 03, 2018 8:53 pm

Thank you for the clarification.

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

Re: Question on kinetic energy

Postby JiangJC Dis2K » Sun Nov 04, 2018 5:01 pm

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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Re: Question on kinetic energy

Postby Mikka Hoffman 1C » Sun Nov 04, 2018 5:29 pm

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
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Re: Question on kinetic energy

Postby Sydney Stump » Sun Nov 04, 2018 5:50 pm

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.


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