//chapter8,Example8_10,pg 185

//condition for dark fringe is 2*t=n*lam

//refer to fig.(e) pg 185

//but B=(lam/(2*alpha*u))

//delt=alpha*x

lam=6000*10^-8

u=1.5

delt=(10*lam)/(2*u)//alpha=lam/(2*B*u), B=x/10

printf("difference t2-t1 from fig.\n")

printf("delt=%.4f cm",delt)