A ray of light is travelling from air to water.What is the angle of incidence in air

From the log table find the value of sin 41⁰ which will be the value ofsin r in the formula

^{put this value  and the value of refractive index 'n' in the formula}

n = sin i/sinr

Now  the value of sin i after converting in degres with the help of log table will give you the desired angle of incidence.

regards

toppers expert.