stdevlin03
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(10) The results shown in the table below were obtained in an experiment to
estimate the Planck's constant (h).

(a) Use the relationship eV =
hc

to calculate a value for the Planck's constant, h

for each LED and hence obtain an average value for h.
(b) Complete the table of results by calculating 1/lambda for each LED and plot a
graph of V against 1/lambda and use the graph to obtain a value for h.Name:  LED - Plancks constant.PNG
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Size:  104.5 KB
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Sinnoh
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(Original post by stdevlin03)
(10) The results shown in the table below were obtained in an experiment to
estimate the Planck's constant (h).

(a) Use the relationship eV =
hc

to calculate a value for the Planck's constant, h

for each LED and hence obtain an average value for h.
(b) Complete the table of results by calculating 1/lambda for each LED and plot a
graph of V against 1/lambda and use the graph to obtain a value for h.Name:  LED - Plancks constant.PNG
Views: 64
Size:  104.5 KB
What exactly do you need help with? What have you managed so far?
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Joinedup
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Wavelength column looks a bit ropey... Should be more like 560 nm for green light.
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stdevlin03
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(Original post by Joinedup)
Wavelength column looks a bit ropey... Should be more like 560 nm for green light.
that's what i was thinking.
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stdevlin03
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(Original post by Sinnoh)
What exactly do you need help with? What have you managed so far?
I answered the full questions but the answers seem so far away from planks they couldn't be right
a) 3.4x10^-38
b)6.4 x10^-33

i feel like the table is wrong
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Sinnoh
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(Original post by stdevlin03)
I answered the full questions but the answers seem so far away from planks they couldn't be right
a) 3.4x10^-38
b)6.4 x10^-33

i feel like the table is wrong
Other than the fact that they've definitely missed out a factor of 10-7 in the wavelength column, I don't see how you could be getting something around 3.4 for the Planck constant - they were all between 6 and 7 when I calculated the values.
Wait, did you think the eV on the left meant 1 electronvolt?
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stdevlin03
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(Original post by Sinnoh)
Other than the fact that they've definitely missed out a factor of 10-7 in the wavelength column, I don't see how you could be getting something around 3.4 for the Planck constant - they were all between 6 and 7 when I calculated the values.
Wait, did you think the eV on the left meant 1 electronvolt?
i think I calculated the EV wrong i used EV = 1/2mv^2
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Sinnoh
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(Original post by stdevlin03)
i think I calculated the EV wrong i used EV = 1/2mv^2
ahh...

eV means electron charge * potential difference, so the formula rearranged for h is h = \dfrac{e \times V \times \lambda}{c}
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stdevlin03
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ohh ill have another go tm thanks
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stdevlin03
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(Original post by Sinnoh)
ahh...

eV means electron charge * potential difference, so the formula rearranged for h is h = \dfrac{e \times V \times \lambda}{c}
for the graph is 6.4x10^-33 close enough or have I plotted it wrong
Edit: after correcting the error in the table there is no longer an issue
Last edited by stdevlin03; 5 months ago
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