What is the Significance of the Y-Intercept in the Graph for Planck's Constant?

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In summary, the conversation revolves around solving for Planck's constant and the work function using the equation Ek=hf-W. The graph provided is a linear function with the x-axis representing threshold frequency and the y-axis representing kinetic energy. The slope of the graph is equal to Planck's constant, and the y-intercept is equal to the negative of the work function. The conversation discusses different approaches to solving for these values, with the mathematical approach being the most straightforward. The conversation also touches on the importance of verifying the accuracy of the experiment and the potential margin of error in the calculated values.
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Homework Statement




Homework Equations


Ek=hf-W


The Attempt at a Solution


Using the equation Ek= hf-W ( W is work function) , in the given graph the x-axis is the threshold frequency so f= 10, and Ek is given by 3ev, i tried to isolate variables but i have no clue what W is equal to

for part c) a stronger force of attraction means greater threshold and kinetic energy so i would imagine a diagonal line going through (0,0) , it would be different in the case that it would start at (0,0) since the cathode ray has a stronger force of attraction.

Im unsure how to go on about doing it , although I believe that the physical signifcance of the y intercept is that it is the negative of the work function .

Homework Statement

 

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  • #2
I'm going to approach this with solely a mathematics prespective.

The graph you have is a linear function, the equation you provided is also in the format of a linear function.

With that alone you've got enough information to solve whatever you're looking for.
 
  • #3
I understand that,as you mentioned its a linear function so assuming the cathode has a stronger force of attraction with its electrons, doesn't it mean that the slope is greater since there is greater attractive force b/w the x-axis ( threshold frequency) and the y -axis( kinetic energy) but how would i determine the value of Planck's constant using
Ek=hf-w
 
  • #4
You have enough information to find everything in that equation from that graph... You should be able to solve for h.
 
  • #5
so h=(Ek+W)/f , the thing is i know that from the given graph f= 3, Ek=3ev and what is W?
 
  • #6
Can't you simply use the slope to "extrapolate" back and find the intercept?
 
  • #7
yes but only thing I am confused is with how to find W still, in the mathematical way not so , but using physics i am
 
  • #8
yes but only thing I am confused is with how to find W still, in the mathematical way not so , but using physics i am

I'm not sure what you're confused about... You can solve it using an "mathematical" approach but you want to solve it using a "physics" approach? What's wrong with using the "mathematical" approach?
 
  • #9
ok I am confused solving mathematically, so basically take the points of 2 points and find the slope after that what would i do, and by doing this would it give me the work function?
 
  • #10
The slope of that graph is Plancks constant.
 
  • #11
okay got that but using the equation i mention Ek=hf-W where "w" represent the work function rearranging for Planck's constant we can solve it using that formula but the only unknown is the work function :S
 
  • #12
You solve Planck's constant by solving the slope. You solve the work function by using Planck's constant.
 
  • #13
we already know Planck's constant though which is 6.63*10^-34Js so why solve Planck's constant when we are finding it?
 
  • #14
Cudi1 said:
we already know Planck's constant though which is 6.63*10^-34Js so why solve Planck's constant when we are finding it?

One good reason is to verify the accuracy of your experiment based on the collected data.
 
  • #15
yes that is true, to verify the validity the only thing that is confusing is finding what the work function is...
 
  • #16
still don't understand would appreciate any help whatsoever
 
  • #17
Okay, if anyone can have a look as mentioned i just find the slope which should give me Planck's constant does it matter that i have a margin error of around 10%? I am getting a value of h=6.7*10^-34, is that ok?
 
  • #18
sorry a slight margin error of approximately 1% is that fine, and is that how i solve by finding the slope which should give me Planck's constant?
 

What is Planck's constant?

Planck's constant, denoted as h, is a fundamental physical constant that relates the energy of a single quantum of a system to its frequency.

Who discovered Planck's constant?

Max Planck, a German theoretical physicist, discovered Planck's constant in 1900. He was studying blackbody radiation and found that the energy of the radiation was directly proportional to its frequency and inversely proportional to Planck's constant.

What is the value of Planck's constant?

The value of Planck's constant is approximately 6.626 x 10^-34 joule-seconds (J·s).

Why is Planck's constant important?

Planck's constant is important because it is a fundamental constant that helps in understanding the behavior of matter and energy at the quantum level. It is also used in various equations and theories, such as the Schrödinger equation and the Heisenberg uncertainty principle.

How is Planck's constant measured?

Planck's constant is measured using different experimental techniques, such as the photoelectric effect, blackbody radiation, and Compton scattering. These experiments involve measuring the energy and frequency of a system and using the formula E = hf, where E is energy, h is Planck's constant, and f is frequency, to calculate the value of h.

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