IPhO 1983 Theoretical Questions
3.Optics – Problem III (7points)
Prisms
Two dispersive prisms having apex angles A ˆ 60 and A ˆ 30 are glued as in the figure below
1 2
(C ˆ 90). The dependences of refraction indexes of the prisms on the wavelength are given by the
relations
b
n a 1 ;
1 1 2
b
n a 2
2 2 2
were
a 1,1, b 1105nm2, a 1,3 , b 5104nm2.
1 1 2 2
a. Determine the wavelength of the incident radiation that pass through the prisms without
0
refraction on AC face at any incident angle; determine the corresponding refraction indexes of
the prisms.
b. Draw the ray path in the system of prisms for three different radiations , ,
red 0 violet
incident on the system at the same angle.
c. Determine the minimum deviation angle in the system for a ray having the wavelength .
0
d. Calculate the wavelength of the ray that penetrates and exits the system along directions
parallel to DC.
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