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### Topic: photoelectric effect  (Read 4810 times)

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#### walkerke

• Guest
##### photoelectric effect
« on: October 11, 2004, 02:04:32 AM »
I am really confused by the photoelectric effect and how to apply it using equations. Here is one of the problems I am having trouble on:  In his explanation of the photoelectric effect, Einstein reasoned that the absorbed photon must have the minimum energy required to dislodge an electron from the metal surface. This energy is called the "work function" of that metal. What is the longest wavelength, in nanometers (nm), of radiation that could cause the photoelectric effect in tantalum, for which the work function is 6.41×10-19 J?

I have tried the equations: E=hnv and E(photon)= hv   where v=frequency. Then I substituded c/wavelength for v but i keep getting the wrong answers. I am really lost.

#### ssssss

• Guest
##### Re:photoelectric effect
« Reply #1 on: October 11, 2004, 05:14:48 AM »
I am really confused by the photoelectric effect and how to apply it using equations. Here is one of the problems I am having trouble on:  In his explanation of the photoelectric effect, Einstein reasoned that the absorbed photon must have the minimum energy required to dislodge an electron from the metal surface. This energy is called the "work function" of that metal. What is the longest wavelength, in nanometers (nm), of radiation that could cause the photoelectric effect in tantalum, for which the work function is 6.41×10-19 J?

I have tried the equations: E=hnv and E(photon)= hv   where v=frequency. Then I substituded c/wavelength for v but i keep getting the wrong answers. I am really lost.

Now i think you are understanding the photoelectric effect the right way.You will be familier with the problems based on it in lesser time.

Whenever the Longest waveleanght is reffered it means the minimum energy wave or photon.Similarly in your numerical you have to find the minimum energy of the photon which can cause the photoelectric effect.Now plancs equation Gives the energy of electromagnetic waveleanth/photon as E=hv.

Here h is the plancks constant which you already know and v is the frequency of photon which is numerically=c/lamda,where c is=3x108m/s and lamda is the waveleanth.

Just substitute all of the values and you will get the result.

Remember longest waveleanth refers to the minimum energy of photon and similarly smallest Frequency also refers to the minima.