//example-5.2
//page no-141
//given
//bragg's angle of reflection
theta1=17.03*(%pi)/180  //radians
//wavelength of light
lambda=0.71  //A
//according to bragg's equation 
//n*lambda=2*d*sin(theta)
//for n=1
d=lambda/2/sin(theta1)  //A
//given that h^2+k^2+l^2=8
//let (h^2+k^2+l^2)^1/2=H
//we get
H=sqrt(8)
a=d*H  //A
//since h^2+k^2+l^2=8 ,hence the reflecting planes will be (220). family of planes (220) include (220), (202), (022) ,etc.