MCQ
When a ray is refracted from one medium to another, the wavelength changes from $6000 \,Å$ to $4000\, Å$. The critical angle for the interface will be
- A${\cos ^{ - 1}}\left( {\frac{2}{3}} \right)$
- B${\sin ^{ - 1}}\left( {\frac{2}{{\sqrt 3 }}} \right)$
- ✓${\sin ^{ - 1}}\left( {\frac{2}{3}} \right)$
- D${\cos ^{ - 1}}\,\left( {\frac{2}{{\sqrt 3 }}} \right)$


