B Einstein's Photoelectric Equation and its graph

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1. Nov 22, 2016

Bloopy

According to the equation, the graph of kinetic energy of emitted photoelectrons from a metal vs the frequency of incident radiation gives a straight line.

My doubt is, what factors does the slope of this line depend on? I think it depends on the nature of metal used. Correct me if I am wrong.

2. Nov 22, 2016

BvU

Hi Bloopy,
It looks as if you know which equation that is. Can you write it up in a post ?

3. Nov 22, 2016

Bloopy

I know this.

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4. Nov 22, 2016

ZapperZ

Staff Emeritus
This is really not an "equation". So let's start all over again. Can you write down the Einstein's photoelectric effect equation?

Zz.

5. Nov 22, 2016

BvU

And what do you think of the mathematical description in the Wikipedia lemma right beside this picture ?

6. Nov 22, 2016

Bloopy

Energy supplied=Work Function + Kinetic Energy

7. Nov 22, 2016

ZapperZ

Staff Emeritus
I am not quite sure why you are being a bit difficult, or if you don't quite know what you are doing.

So, if I write this:

Ek = hf - φ

where Ek is the maximum kinetic energy of the photoelectrons, h is the Planck constant, f is the frequency of light, and φ is the work function, do you understand that this is the photoelectric effect equation, similar to what you wrote, or do you need an explanation for this?

Zz.

8. Nov 22, 2016

Bloopy

I am on the same page as you

9. Nov 22, 2016

ZapperZ

Staff Emeritus
Not sure what page you're on, but OK.

Now, I will make the assumption that you know the mathematics for the equation of a straight line, i.e.

y = mx + b

so, I will not explain the meaning of that equation (this is the math that you should already know by the time you tackle this physics).

The graph you referred to in your original post is a graph of Ek versus f, i.e. Ek plotted in the vertical axis, and f in the horizontal axis. Make a visual identification of these two equations:

y = mx + b
Ek = hf - φ

If you identify

y→Ek

and

x→f

then what corresponds to the slope of the line? As a bonus, what corresponds to the y-intercept of the line?

Zz.

Last edited: Nov 23, 2016