Question

For students P, Q, R and S traced the path of a ray of light passing through a glass slab for an angle of incidence ${40}^{\circ }$ and measured the angle of refraction. The values as measured them were ${18}^{\circ };{22}^{\circ };{25}^{\circ }$ and ${30}^{\circ }$ respectively. The student who has performed the experiment methodically is

• A. P
• B. Q
• C. R
• D. S

Answer 1

The correct option is C

R

The student R has performed the experiment methodically. The reason can be explained using Snell's law.
According to Snell's law,
$\frac{sini}{sinr}={\mu }_g$
Here,
i = Angle of incidence
r = Angle of refraction
${\mu }_g$= Refractive index for glass
The angle of refraction measured by student R is most appropriate as it verifies the Snell's law.
Given:
$i={40}^{\circ }$
The angle of refraction measured by student R, $r={25}^{\circ }$
Also,
$sin{40}^{\circ }=0.642$
$sin{25}^{\circ }=0.422$
Now,
$\frac{sin{40}^{\circ }}{sin{25}^{\circ }}=\frac{0.642}{0.422}=1.52$
The refractive index for glass is 1.5; it verifies the result derived above.
Hence, the correct option is C.
Disclaimer: The values of $sin{40}^{\circ }$ and $sin{25}^{\circ }$ can be obtained using trigonometric tables.