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Three thin prisms are combined as shown in figure. The refractive indices of the crown glass for red, yellow and violet rays are mu_r, mu_y and mu_v respectively and those for the flint glass are mu_r^', mu_y^r and mu_v^' respectively. Find the ratio A'/A for which (a) there is no net angular dispersion, and (b) there is no net deviation in the yellow ray. |
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Answer» `delta_y = delta_(EY) - delta_(ty)` ` =2 delta_(ey) - 2delta_(ry)` `= 2 (mu_y + 1)A - (mu_(re) -1)A` Similarlyuthe ANGULAR dispersion produced by the combination is `(a) For net angular dispersion to be ZERO, `delta_t - delta_t = 0 =2 (mu_(upsilon c) - mu_(tc)A` `=(mu_(upsilon t) - mu_(rt)A` rArr (A)/(A) = (2(mu_(upsilon c) - mu_(r c)`/((mu_(upsilon c) - uu_rc)` `= (2(mu_r - u_r))/((mu_r - mu))` (b) Fro net deviation in the yellow ray to be zero, `DELTA = -0` `rArr 2(mu_(CY) -1)A = (2(mu_(cy) -1))/((mu_(ty) -1))` `=(2(mu_y -1))/((mu_y -1))` |
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