Laws of Refraction

Q.

Total Internal reflection happens only when light is travelling from an optically denser medium to an optically rarer medium.

1. True
2. False

Q.

In Snell’s law,

$\frac{\sin i}{\sin r}$ = $\frac{v_1}{v_2}$ = constant
This constant is called as:

1. reflective index

2. refractive index

3. none of these

4. light index

Q. The incident ray, the refracted ray and the normal at the point of incidence all lie _____.

1. in different planes
2. in the same plane
3. in mutually perpendicular planes
4. at an angle of ${45}^{\circ }$ to each other

Q.

How is refractive index of a medium 2 given with respect to medium 1 related to speed of light?
where, $n_1$ and $n_2$ are the respective refractive indicies of medium 1 and medium 2. And, $c_1$ and $c_2$ are speed of light in medium 1 and medium 2 respectively.

1. 

2. 

3. None of these

4. n₁ – n₂ = v₂ – v₁

Q. Explain laws of reflection. [3 Marks]

Q. A ray of light is incident at ${60}^{\circ }$, on glass-air interface. Then the light ray will ___. (Given: Incident ray lies in glass).
Use : [${\mu }_g$ = $\sqrt{2}$ , ${\mu }_a$ = 1]

1. pass undeviated

2. reflect back into glass

3. refract at ${90}^{\circ }$ to the normal

4. refract at ${60}^{\circ }$ to the normal

Q. Critical angle for a light ray travelling from denser to rarer medium is defined as the angle of incidence at which the angle of refraction is 90°.
If a ray of light travels from water $\left({\mu }_w\right)$ to air $\left({\mu }_a\right)$. Find the critical angle?

1. ${\sin }^{-1}\left(\frac{{\mu }_w}{{\mu }_a}\right)$

2. ${\sin }^{-1}\left(\frac{{\mu }_a}{{\mu }_w}\right)$

3. ${\cos }^{-1}\left(\frac{{\mu }_w}{{\mu }_a}\right)$

4. ${90}^{\circ }$

Q.

Given that i is angle of incidence and r is angle of refraction for a light ray at a boundary, the correct expression for Snell's Law is:

1. $\sin i={\sin }^{2}r$

2. $\sin i=k\sin r$
   [where k = constant]

3. $\cos i=k\cos r$
   [k = constant]

4. $\sin r={\sin }^{2}i$

Q.

A ray of light coming from a denser medium does not enter rarer medium and reflects back. This phenomenon is called ___.

1. dispersion of light

2. total internal reflection

3. total internal refraction

4. refraction

Q. 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)

1. $n_{air}$ $Sin{\theta }_{air}$ = $n_{water}$ $Sin{\theta }_{water}$
2. $n_{air}$ $Sin{\theta }_{water}$ = $n_{water}$ $Sin{\theta }_{air}$
3. $n_{air}$ $Sin{\theta }_{air}$ $n_{water}$ $Sin{\theta }_{water}$ = 1
4. $n_{air}$ $n_{water}$ = $Sin{\theta }_{water}$ $Sin{\theta }_{air}$