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Question
Choose the correct option.
Angles of deviation for extreme colours are given for different prisms. Select the one having maximum dispersive power of its material.
Options
7°, 10°
8°, 11°
12°, 16°
10°, 14°
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Solution
7°, 10°
Explanation:
Dispersive power for thin prism is,
ω = `(δ_"V"-δ_"R")/(((δ_"V"+δ_"R")/2)`
∴ For values in option (A),
ω = `(10-7)/(((10+7)/2))=6/17` = 0.35
For values in option (B),
ω = `(11-8)/(((11+8)/2))=6/19` = 0.31
For values in option (C),
ω = `(16-12)/(((16+12)/2))=2/7` = 0.28
For values in option (D),
ω = `(14-10)/(((14+10)/2))=1/3` = 0.33
Thus, value of ω is maximum for prism with angles of deviations, 7°, 10°.
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