A plane glass plate is placed over a various coloured letters (violet, green, yellow, red). The
letter which appears to raised more

The refractive index of glass plate is different for different colours because the frequency or wavelength is different for
different colours.
This refractive index is maximum for violet colour and minimum for red colour.
Now, apparent depth \( =\frac{\text { real depth }}{\text { refractive index }} \)
Therefore, violet letter appears to be raised more