# Determining plancks constant

Watch
Announcements
#1
(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.
0
5 months ago
#2
(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.
What exactly do you need help with? What have you managed so far?
1
5 months ago
#3
Wavelength column looks a bit ropey... Should be more like 560 nm for green light.
0
#4
(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.
0
#5
(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
0
5 months ago
#6
(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?
0
#7
(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
0
5 months ago
#8
(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 is
0
#9
ohh ill have another go tm thanks
0
#10
(Original post by Sinnoh)
ahh...

eV means electron charge * potential difference, so the formula rearranged for is
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
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### Poll: What factors affect your mental health most right now? Post-lockdown edition

5.32%
Uncertainty around my education (65)
11.52%
Uncertainty around my future career prospects (66)
11.7%
Lack of purpose or motivation (75)
13.3%
Lack of support system (eg. teachers, counsellors, delays in care) (32)
5.67%
Impact lockdown had on physical health (28)
4.96%
Social worries (incl. loneliness/making friends) (60)
10.64%
Financial worries (35)
6.21%
Concern about myself or my loves ones getting/having been ill (22)
3.9%
Exposure to negative news/social media (34)
6.03%
Difficulty accessing real life entertainment (15)
2.66%
Lack of confidence in making big life decisions (56)
9.93%
Worry about missed opportunities during the pandemic (46)
8.16%