CBSE Class 12-science Answered

1)to remove the chromatic aberration the combination of lenses should be.                                                whare( Fr and Fv represent the equivalent focal length of the combination for red and violet colours).                                                                                                                                                                                                                                                             2)an achromatic telescope objective is to be made by combining the lenses of flint and crown glasses.this proper choice is (ans.convergent of crown and divergent of flint) how? pls explain it.                                                                                                                                             3)an equilateral prism is placed on the prism table of spectrometer in the position of minimum deviation .if the angle of incidence is 60,the angle of deviation of the ray is (ans.60)