Photoelectric Effect Equations

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Doreen Liu 4D
Posts: 54
Joined: Wed Sep 11, 2019 12:17 am

Photoelectric Effect Equations

Postby Doreen Liu 4D » Thu Oct 17, 2019 6:13 pm

The velocity of an electron from a metal surface by a photon is 3.6 x 10^3 km/s. What is the wavelength of ejected e-?
For this question, since wavelength can be calculated by both h/mv and hc/E, how do I determine which one to use?

Posts: 50
Joined: Fri Aug 02, 2019 12:15 am

Re: Photoelectric Effect Equations

Postby Mansi_1D » Thu Oct 17, 2019 6:18 pm

You would use h/mv to find the wavelength because velocity is given and you know what h and m are.

Megan Jung 3A
Posts: 50
Joined: Thu Jul 11, 2019 12:17 am

Re: Photoelectric Effect Equations

Postby Megan Jung 3A » Thu Oct 17, 2019 7:40 pm

Since you are given the velocity (v)=3.6 x 10^3 km/s, and it is known that the mass of an electron is 9.1 x 10^-31kg I would us the equation
Wavelength = h/mv.

Jacey Yang 1F
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

Re: Photoelectric Effect Equations

Postby Jacey Yang 1F » Thu Oct 17, 2019 8:11 pm

h/mv is used to find the wavelength of one moving particle with momentum p, in this case an electron. hc/E calculates the wavelength of the light needed to eject an electron.

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