I was doing my hw for chemistry and I could not possibly figure out a question which I thought was simple. I got it wrong but it is really frustrating and I want to know the answer. So I hope someone can help me out. Here is the q:

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 (nm), of radiation that could cause the photoelectric effect in barium for which the work function is 4.30E-19 J?

So, E=hc/wavelength h=6.26E-34 Js and c=3E8 m/s

I thought to set E= the work function and solve for the wavelength but I was incorrect.

well, this forum is primarily about drugs, im gonna move it to Mad Scientists and see if they can help you better. we're all burnouts and stoners

It means that only certain wavelenths of light are stonge enough to move an electron, you could shine an extremely bright red light at sodium and nothing would happen, but if even a weak yellow like is shone at sodium the elctrons will fly off.
This is compared to some balls, if you have a bowling ball(electron) and you throw a pingpong ball(red light) at it it wont move, even if you throw a whole lot of pingpong balls(intensce red light) it still wont move. Now if you throw a basball(yellow light) it will move the bowling ball(electron). I hope that helps if you need to know somthing eles just ask but dont put that scientific mumbo jumbo in it, it just confuses me.

CTR

I understand what the photoelctric effect is, but I don't understand the calculations to derive the answer to the question.

Are you trying to find the amount of energy in one photon of light?

CTR

No, Genital. He's asking how to find the wavelength of light which has at least a specific energy. Read his question again, then heed your own advice and stay quiet.

Whats your problem theta im just trying to help him out,

Im not sure what you mean once again but ill try anyway im going to use Na thought its a bit easyer and i dont want to do your homeworks for you,
Y=lambda,

To calculate the wavelenth of light emted by Na if the frequnce of the radiation is 5.10 *10^14/s.

y= 3.00 * 10^10cm/s-----speed light
-----------------
5.10 * 10^14/s ------Frequency of Na

You now would calcle out both s, and divide
the answer you should get is 5.88 * 10^-5 cm.

CTR


[This message has been edited by Genital-Warfare (edited 10-14-2002).]

Hey lokisdaki, you assumed correct. all you should ahve to do is solve

wavelength = hc/workfunction

I get 4.37e-7 m for an answer

I figured 4.37E-7 m, or 4.37E-16 nm. But this is not the correct answer apparently.

I tutor highschool physic and as you described the problem that is the correct answer. If it's not the answer they give you, then either question their answer or reread the problem and see if you are missing something.

I found your problem h = 6.63e-34 not 6.26e-34

the new answer is
4.63e-7 m or 4.63e-16 nm