A thin prism `P_1` of angle `4^0` and refractive index 1.54 is combined with another thin prism `P_2` of refractive index 1.72 to produce dispersion without deviation.The angle of prism `P_2` is

A thin prism P of refracting angle 3^(@) and refractive index . 1.5 is combined with another thin prism Q of refractive index 1.6 to produce dispersion without deviation. Then the angle of prism Q is

A thin prism P of refracting angle 3^(@) and refractive index . 1.5 is combined with another thin prism Q of refractive index 1.6 to produce dispersion without deviation. Then the angle of prism Q is

A thin prism P_(1) with angle 6^(@) and made from glass of refractive index 1.54 is combined with another thin prism P_(2) of refractive index 1.72 to produce dispersion without deviation. The angle of prism P_(2) will be

A thin prism P_(1) with angle 6^(@) and made from glass of refractive index 1.54 is combined with another thin prism P_(2) of refractive index 1.72 to produce dispersion without deviation. The angle of prism P_(2) will be