Bukhovtsev-et-al-Problems-in-Elementary-Physics

424 ANSWERS AND SOLUTIONS
dering triangle AS t B, we can write
Hence,
I
2+aa~aan
l::r:2aa (n- 1)
Fig. 554
By using the solution of Problem 764, we find:
'AD l (a+b)
~h= 2aa(n_l)=O.15cm
L
771. N = Ah' where L i$ the width of the interference pattern.
It cen be seen from Fig.· 256 that L=.! t, where I is the distance between
a
the virtual images 8 1 and'S. of the source.
Using the results ·of the previous problem, w~ get
4aba 2 (n -1)2
N= (a+b) A e!5
772. A biprism made of a substance with a refraction index n 2 deflects
rays by an angle
CPt=( 90"- ~ ) (n,- nl)
where nl is the refraction index of the medium from which the rays fall. For
a biprism in air
If the biprisms are equivalent, CPt = cp"
Hence,
~=~ n,-n1+ IS0 0 nt-l
n,-I I'lt- I
For the values given in the initial conditions, 6:!: 179°37'.