Question

A beam of red light ($7000$ A.U. in air) is passing from air into a medium making an angle of incidence of ${61}^o$ and angle of refraction of ${34}^o$. find the wavelength of red light in the medium.

• A. $1475.7A^o$.
• B. $5475.7A^o$.
• C. $4475.7A^o$
• D. $6475.7A^o$.

Answer 1

The correct option is C $4475.7A^o$

From Snell law we know,

$=>\frac{\sin {\theta }_1}{\sin {\theta }_2}=\frac{{\mu }_2}{{\mu }_1}\frac{{\mu }_2}{{\mu }_1}=\frac{\sin {61}^0}{\sin {34}^0}=\frac{0.8746}{0.5591}=1.5642$

Again we know

$\frac{{\mu }_m}{{\mu }_a}=\frac{v_a}{v_m}=\frac{\frac{wavelengthoflightinair}{time}}{\frac{wavelengthoflightinmedium}{time}}wavelengthoflightinmedium=\frac{v_a}{\frac{{\mu }_m}{{\mu }_a}}=\frac{7000}{1.5642}=4475.13A.U$