Hi friends, Please help me in answering this problem The problem is as follows, https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-ash3/s480x480/557923_2937818221818_1718139220_n.jpg Well, As far as I am concerned, When white light fall on the first surface, after refraction through it, the ray will be deviated. But the glass material will have different refractive indexes for the seven colors (VIBGYOR)of light. Hence they will deviate at different angles of deviations. And Violet will be at the lowest position on the screen. And after the second refraction from the second surface, all the rays will go parallel to the initial light ray again. Hence after the two refractions the light will split into seven colors. And the ray diagram would be like this - https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-prn1/s480x480/11334_2937788181067_1369934100_n.jpg Hence the answer should be option (C) But book says answers of the question are option (B) & (C). Please friends help me in solving this problem. Thanks to all in advance.