The respective angles of the flint and crown glass prisms are A’ and A. They are to be used for dispersion without deviation, then the ratio of their angles A' /A will be

• A

  $-\frac{\left({\mathrm{\mu }}_{\mathrm{y}}-1\right)}{\left({\mathrm{\mu }}_{\mathrm{y}}^{\mathrm{\prime }}-1\right)}$

• B

  $\frac{\left({\mathrm{\mu }}_{\mathrm{y}}^{\mathrm{\prime }}-1\right)}{\left({\mathrm{\mu }}_{\mathrm{y}}-1\right)}$

• C

  $\left({{\mathrm{\mu }}_{\mathrm{y}}}^{\mathrm{\prime }}-1\right)$

• D

  $\left({\mathrm{\mu }}_{\mathrm{y}}-1\right)$