// Scilab code Exa7.14: : Page-297 (2011)
clc; clear;
g = 9.8;            // Acceleration due to gravity, metre per square sec
c = 3e+08;                // Velocity of light, metre per sec
y = 20;                // Vertical distance between source and absorber, metre
delta_v = g*y/c^2;        // Frequency shift
printf("\nThe required frequency shift of the photon = %4.2e ", delta_v);

// Result
// The required frequency shift of the photon = 2.18e-015