IPhO 1983 Theoretical Question III MARKING SCHEME FOR ANSWERS TO THE THEORETICAL QUESTION III -OPTICS Marking scheme – Prisms Page 1 of 3 IPhO 1983 Theoretical Question III Marking scheme – Prisms Page 2 of 3 Part MARKING SCHEME - THE THEORETICAL QUESTION III - PRISMS Total Scores III. a. For: ( ) ( ) 0201 λλ nn = 0.50p 12 21 0 aa bb − − = λ 0.25p final result: nm500 0 = λ 0.25p ( ) ( ) 5,1 0201 == λλ nn 0.25p 1.25 points III. b. For the rays with different wavelength ( ioletred v λλλ ,, 0 ) having the same incidence angle on first prism, the paths are illustrated in the figure III.1 Figure III.1 2.00 points III. c. For: ( ) ( ) 2 ' sin 2 ' sin min 0201 A A nn + == δ λλ 0.25p ( ) °= 30' ˆ Am 0.25p 2 ' 2 ' sin 2 3 arcsin2 min AA − ⋅= δ 0.25p final result: °≅ 7,30 min δ 0.25p 1.00 point III. d. For: the refraction law on the AD face 111 sinsin rni ⋅= 0.25p Figure III.2 the refraction law on the AC face 2211 sin'sin rnrn ⋅=⋅ 0.25p 111 ' Arr =+ 0.25p 22 Ar = 0.25p °= 30 1 i 0.25p 1 122 2 1 sin cossin2 14 A AAn n +⋅ =− 2.75 points IPhO 1983 Theoretical Question III Professor Delia DAVIDESCU, National Department of Evaluation and Examination– Ministry of Education and Research- Bucharest, Romania Professor Adrian S.DAFINEI,PhD, Faculty of Physics – University of Bucharest, Romania Marking scheme – Prisms Page 3 of 3