Question

For a light ray passing from air to water, according to Snell's law:
($n$ represents refractive index of the medium, ${\theta }_{air}$ is the angle of incidence and ${\theta }_{water}$ is the angle of refraction)

• A. $n_{air}$ $Sin{\theta }_{air}$ = $n_{water}$ $Sin{\theta }_{water}$
• B. $n_{air}$ $Sin{\theta }_{water}$ = $n_{water}$ $Sin{\theta }_{air}$
• C. $n_{air}$ $Sin{\theta }_{air}$ $n_{water}$ $Sin{\theta }_{water}$ = 1
• D. $n_{air}$ $n_{water}$ = $Sin{\theta }_{water}$ $Sin{\theta }_{air}$

Answer 1

The correct option is A $n_{air}$ $Sin{\theta }_{air}$ = $n_{water}$ $Sin{\theta }_{water}$

According to Snell's law, for a light ray travelling from one medium to another, the ratio of sines of angle of incidence to the angle of refraction is a constant. This constant is the refractive index of medium 2 with respect to medium one.
Here,
$n_{air}$ $sin{\theta }_{air}$ = $n_{water}sin{\theta }_{water}$ or $\Rightarrow \frac{Sin{\theta }_{air}}{Sin{\theta }_{water}}=\frac{n_{water}}{n_{air}}$ correctly represents Snell's law.