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%  Script file: c14_date.m 
% 
%  Purpose:  
%    To calculate the age of an organic sample from the percentage  
%    of the original carbon 14 remaining in the sample. 
% 
%  Record of revisions: 
%      Date       Programmer          Description of change 
%      ====       ==========          ===================== 
%    12/02/97    S. J. Chapman        Original code  
% 
% Define variables: 
%   age       -- The age of the sample in years 
%   lamda     -- The radioactive decay constant for carbon-14, 
%                in units of 1/years. 
%   percent   -- The percentage of carbon 14 remaining at the time 
%                of the measurement 
%   ratio     -- The ratio of the carbon 14 remaining at the time 
%                of the measurement to the original amount of  
%                carbon 14. 
 
% Set decay constant for carbon-14 
lamda = 0.00012097;             
 
% Prompt the user for the percentage of C-14 remaining. 
percent = input('Enter the percentage of carbon 14 remaining:\n'); 
 
% Perform calculations 
ratio = percent / 100;             % Convert to fractional ratio 
age = (-1.0 / lamda) * log(ratio); % Get age in years 
 
% Tell the user about the age of the sample. 
string = ['The age of the sample is ' num2str(age) ' years.']; 
disp(string);