Post by: dgt20 on 02/03/2018 02:54:39
Post by: chris on 02/03/2018 07:29:01
Nt = N0e-λt
...where N0 is the number of nuclei you are starting with and λ is the decay constant with units s-1
So you can write a simple recurring formula that substitutes for t over the range of values that you want to test.
Does that help?
Post by: dgt20 on 02/03/2018 08:17:15
The formula for the number of decayable nuclei Nt remaining after time t is given by:
Nt = N0e-λt
...where N0 is the number of nuclei you are starting with and λ is the decay constant with units s-1
So you can write a simple recurring formula that substitutes for t over the range of values that you want to test.
Does that help?
I understand the equation however i don't know how to plug in the decay constant in excel? I just dont know how to graph/do this on excel.
Post by: Bored chemist on 02/03/2018 14:23:24
Post by: dgt20 on 02/03/2018 23:35:25
Are you trying to replicate the dice experiment in excel?
I want to compare decay results from dice experiment to decay using the decay constant on excel
Post by: evan_au on 03/03/2018 10:24:36
I simulate 16 dice -
- Each row represents one half life, numbered in Column A
- Column B shows the theoretical number present after this many half-lives. Note that this number becomes a fraction, while real dice can't become a fraction.
- if the dice face shows a number > 3, it continues into the next round.
- Column C counts how many dice are left
- Press F9 to recalculate (start with the full number of dice again)
- The results are slightly different every time you press F9
- You can experiment with more dice by duplicating column S in more columns to the right.
- There is a similar experiment on the "Coin" worksheet, simulating flipping a lot of coins. Only half of them are left after a half-life.
But I can't upload EXCEL files.
Download the file to disk, then remove the JPG suffix.
Scan with a virus scanner. Then it should open in EXCEL.
Dice_Sim.xlsx.jpg (26.99 kB - downloaded 470 times)
Post by: dgt20 on 03/03/2018 10:45:04
Ok, I've had a go...
I simulate 16 dice -
- Each row represents one half life, numbered in Column A
- Column B shows the theoretical number present after this many half-lives. Note that this number becomes a fraction, while real dice can't become a fraction.
- if the dice face shows a number > 3, it continues into the next round.
- Column C counts how many dice are left
- Press F9 to recalculate (start with the full number of dice again)
- The results are slightly different every time you press F9
- You can experiment with more dice by duplicating column S in more columns to the right.
- There is a similar experiment on the "Coin" worksheet, simulating flipping a lot of coins. Only half of them are left after a half-life.
But I can't upload EXCEL files.
Download the file to disk, then remove the JPG suffix.
Scan with a virus scanner. Then it should open in EXCEL.
edit: nvm
Post by: chris on 03/03/2018 11:01:14
But I can't upload EXCEL files.
Hi @evan_au - I've not tried it with Excel, but it should let you send files as attachments in PMs - see this upgrade note: https://www.thenakedscientists.com/forum/index.php?topic=70438.msg517348#msg517348
Let me know if it works please.
Post by: alancalverd on 03/03/2018 11:26:28
Put your starting number into a cell, say B2. I always start with B2 to give me space for annotations.
In B3 write =B2*exp(-L)
Now use autofill to give values for B4.....BN where N is as large as you like.
You can calculate the half life t½ = ln2/L = 0.693/L and compare it with the graphical value.
The half-life or decay constant you use depends on how you want to reject the dice, usually either 1/6 per throw or 1/2 per throw. 1/6 will give you a smoother curve and a better fit between experiment and calculation - just like real life where measuring short halflives is much more difficult!.
Post by: chris on 03/03/2018 15:51:00
@evan_au - since posting, I've checked the PM attachments settings and .xls and .xlsx files are both permitted in PM attachments.But I can't upload EXCEL files.
Hi @evan_au - I've not tried it with Excel, but it should let you send files as attachments in PMs - see this upgrade note: https://www.thenakedscientists.com/forum/index.php?topic=70438.msg517348#msg517348
Let me know if it works please.
Obviously, users should always screen attachments before they execute things on their local machine.
Post by: evan_au on 04/03/2018 09:20:16
I tried putting an attachment on a PM (Personal Message) like the one in the link, and it didn't bring up the "Choose File" button?
[ Invalid Attachment ] [ Invalid Attachment ]
Am I looking in the wrong place?
Post by: dgt20 on 04/03/2018 11:43:22
Define your decay constant L
Put your starting number into a cell, say B2. I always start with B2 to give me space for annotations.
In B3 write =B2*exp(-L)
Now use autofill to give values for B4.....BN where N is as large as you like.
You can calculate the half life t½ = ln2/L = 0.693/L and compare it with the graphical value.
The half-life or decay constant you use depends on how you want to reject the dice, usually either 1/6 per throw or 1/2 per throw. 1/6 will give you a smoother curve and a better fit between experiment and calculation - just like real life where measuring short halflives is much more difficult!.
Using decay formula Nt = N0e-λt, I replaced decay constant with 0.166 (dice 1/6 chance) then compared to the results of the formula N=1000(1-1/6)^t (time). Would this be a fair comparison of expected dice vs expect dice decay results?
Post by: alancalverd on 04/03/2018 13:42:04
N=1000(1-1/6)^tis rearranged as
N = 833.33t, which increases with t and is very different from N = 1000/eλt, which decreases with t.
If you use the Excel algorithm I suggested above, Np = ROUND (Np-1* 0.833, 0) you will get a succession of integers that look like idealised dice and behave very much like the decay of 100000 nuclei. Real dice will give you a rougher curve because you may get any number of sixes on a single throw, but we get the same effect with very small (10000 or less) numbers of real nuclei due to Geiger counter dead time limitations.
Post by: chris on 05/03/2018 15:59:26
The "trick" of putting a dummy "JPG" suffix should work in delivering the EXCEL file via a post.
I tried putting an attachment on a PM (Personal Message) like the one in the link, and it didn't bring up the "Choose File" button?
Am I looking in the wrong place?
Hello Evan - I've reset the permissions for the application. It might be that they had been suspended when the forum was rebuilt in January.
I've tested successfully, I think, PM'ing you a picture and a spreadsheet.
The file selection / attachment box now appears below the PM message body input box:
screen_shot.PNG (49.33 kB . 1152x779 - viewed 14030 times)