Question

When light travels from a rarer to a denser medium, its speed :

• A. increases
• B. decreases
• C. remains same
• D. cant say

Answer 1

The correct option is B decreases

According to Snell's Law: $\frac{n_2}{n_1}=\frac{v_1}{v_2}$
Denser medium will have refractive index $n_2$ greater than refractive index $n_1$ of rarer medium. Thus, according to the law, speed will decrease while travelling from rarer medium to denser i.e. $v_2$ will be lesser than $v_1$