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// Scilab Code EX3.44:: Page-3.57 (2009)
clc;clear;
w = 2; // Width of the grating, cm
P = 4500; // Total number of lines on the grating
a_plus_b = w/P; // Grating element, cm
lambda1 = 5890e-008; // Wavelength of sodium D1 line, cm
lambda2 = 5896e-008; // Wavelength of sodium D2 line, cm
lambda = (lambda1+lambda2)/2; // Mean wavelength of light used, cm
d_lambda=lambda2-lambda1; // Difference in wavelengths of D-lines of sodium, cm
n = 2; // Order of diffraction
// As a_plus_b*sind(theta)=n*lambda, solving for theta
theta = asind(n*lambda/a_plus_b); // Angle of diffraction, degrees
DP = n/(a_plus_b*cosd(theta)); // Dispersive power of grating
d_theta = DP*d_lambda*180/%pi; // Angular separation between D-lines, degrees
RP = lambda/d_lambda; // Required resolving power of grating for sodium lines
N = 2.54/a_plus_b; // No. of lines per cm on grating, lines/cm
RP_cal = n*N; // Calculated resolving power of grating
printf("\nThe angle of diffraction for maxima in second order = %6.4f degrees", d_theta);
printf("\nAs %5.3e > %3d, D-lines can be resolved.", RP_cal, RP);
// Result
// The angle of diffraction for maxima in second order = 0.0160 degrees
// As 1.143e+04 > 982, D-lines can be resolved.
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