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### Energy Problem

Posted: Sun Oct 06, 2019 5:12 pm
Does anyone know how to solve this problem: Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 1015 s-1 before it can emit an electron from its surface. What is the minimum energy needed to produce this effect?

### Re: Energy Problem

Posted: Sun Oct 06, 2019 5:52 pm
Hi there,

I solved the problem by plugging the minimum frequency into the equation E (energy) = h (Planck's constant, 6.626 * 10^-34) x v (wavelength). When I multiplied Planck's constant by the minimum frequency I got 7.22 x 10-19 J, which is the correct answer! I hope this helps :)

-Rebecca

### Re: Energy Problem

Posted: Tue Oct 08, 2019 11:23 pm
To add on, you would use the equation E=hv because this equation calculates the energy of a photon. In order for an electron to be ejected, the incoming photon's energy must be equal to or greater than the energy needed to remove the electron (work function). Therefore, finding the minimum energy of the incoming photon would be finding the minimum energy needed to eject the electron.

### Re: Energy Problem

Posted: Thu Oct 10, 2019 11:28 am
To eject an electron from the surface of a metal, the incoming photo must have enough energy. Given the frequency, we can use the Einstein Equation E=hv to solve for energy E. Plug the frequency and the constant h, the resulting value will be the minimum energy required.

### Re: Energy Problem

Posted: Thu Oct 10, 2019 11:43 am
Use the formula E=hv. We know that h is planck's constant (6.626*10^-34 m^2kg/s) and that v is frequency (1.09 x 10^15 s-1). If we plug these into the equation, we get E = (6.626*10^-34) (1.09 x 10^15) = 7.22 x 10^-19 J. Using the minimum frequency will also give the minimum amount of energy.