TIR

Q. In total internal reflection, when the angle of incidence is equal to the critical angle for the pair of media in contact, what will be angle of refraction ?

1. $180°$
2. $0°$
3. equal to angle of incidence
4. $90°$

Q. A ray of light is incident at an angle i from denser to rare medium. The reflected and the refracted rays are mutually perpendicular. The angle of reflection and the angle of refraction are respectively r and r’, then the critical angle will be

1. $si{n}^{-1}\left(sinr\right)$
2. $si{n}^{-1}\left(tan{r}^{\prime }\right)$
3. $si{n}^{-1}\left(tani\right)$
4. $ta{n}^{-1}\left(sini\right)$

Q. In total internal reflection, laws of reflection hold true.

1. True
2. False

Q. A beam of light consisting of red, green and blue colours is incident on a right angled prism. The refractive index of the material of the prism for the red, green and blue colours are $1.39$, $1.44$ and $1.47$ respectively. The prism will

1. separate the red colour from the green and blue colours
2. separate the blue colour from the red and green colours
3. separate all the three colours from one another
4. not separate the three colours at all

Q. A light ray is incident on a transparent sphere of index $=\sqrt{2}$ , at an angle of incidence $={45}^{\circ }$. What is the deviation of a tiny fraction of the ray, which enters the sphere, undergoes two internal reflections, and then refracts out into air?

1. ${270}^{\circ }$
2. ${240}^{\circ }$
3. ${120}^{\circ }$
4. ${180}^{\circ }$

Q. A rod made of glass, refractive index $1.5$ and of square cross section, is bent into the shape shown in figure. A parallel beam of light falls normally on the plane flat surface $A$. Referring to the diagram, $d$ is the width of a side and $R$ is the radius of inner semicircle. Find the maximum value of ratio $\frac{d}{R}$ so that all light entering the glass through surface $A$ emerges from the glass through surface $B$.

1. $\frac{1}{2}$
2. $\frac{1}{5}$
3. $\frac{1}{4}$
4. $\frac{2}{3}$

Q. A ray light travelling in the direction $\frac{1}{2}(\hat{i}+\sqrt{3}\hat{j})$ is incident on a plane mirror. After reflection, it travels along the direction $\frac{1}{2}(\hat{i}-\sqrt{3}\hat{j})$.The angle of incidence is

1. ${60}^{\circ }$
2. ${30}^{\circ }$
3. ${40}^{\circ }$
4. ${75}^{\circ }$

Q. TIR occurs when light passes from rarer medium to denser medium.

1. False
2. True

Q. A light ray from air is incident (as shown in figure) at one end of a glass fiber (refractive index m = 1.5) making an incidence angle of 60^o on the lateral surface, so that it undergoes a total internal reflection. How much time would it take to traverse the straight fiber of length 1 km
​

1. $3.33\mu sec$
2. $6.67\mu sec$
3. $5.77\mu sec$
4. $3.85\mu sec$

Q. A light ray goes from a medium of refractive index$\sqrt{2}$ to a medium of refractive index 1. The minimum angle of incidence for TIR to happen is .

1. ${30}^{\circ }$
2. ${45}^{\circ }$
3. ${60}^{\circ }$
4. ${90}^{\circ }$

Q. A fish looking up through the water sees outside world contained in a circular horizon. The refractive index of water is $\frac{4}{3}$ and the fish is $12\text{cm}$ below the surface. The radius of this circle in $\text{cm}$ is

1. $36\sqrt{7}$
2. $\frac{36}{\sqrt{7}}$
3. $36\sqrt{5}$
4. $4\sqrt{5}$

Q. Critical angle of glass is ${\theta }_1$ and that of water is ${\theta }_2$. The critical angle for water and glass surface would be $({\mu }_g=\frac{3}{2},{\mu }_w=\frac{4}{3})$

1. Less than ${\theta }_2$
2. Between ${\theta }_{1}and{\theta }_2$
3. Greater than ${\theta }_2$
4. Less than ${\theta }_1$

Q. A light ray in medium (Refractive index $=5/3$) making an angle of ${30}^{\circ }$ with normal, enters another medium. The angle in other medium is ${\sin }^{–1}\left(5/6\right)$. How many minimum degrees the incident angle must be increased such that the ray is completely reflected.

Q.

Light is going from some denser medium to air. The refractive index of the medium is 1.7. Calculate the angle of incidence, such that if it is further increased, total internal reflection will occur in medium I.

1. $si{n}^{-1}\left(\frac{1}{\sqrt{3}}\right)$
2. $si{n}^{-1}\left(\frac{1}{\sqrt{2}}\right)$
3. $si{n}^{-1}\left(\frac{1}{\sqrt{5}}\right)$
4. Such an angle of incidence can't be calculated

Q. A light ray goes from a medium of refractive index$\sqrt{2}$ to a medium of refractive index 1. The minimum angle of incidence for TIR to happen is .

1. ${30}^{\circ }$
2. ${45}^{\circ }$
3. ${60}^{\circ }$
4. ${90}^{\circ }$

Q. The velocity of light in a medium is half its velocity in air. If ray of light emerges from such a medium into air, the angle of incidence, at which it will be totally internally reflected, is

1. ${15}^{\circ }$
2. ${30}^{\circ }$
3. ${25}^{\circ }$
4. ${35}^{\circ }$

Q. A fish looking from within water sees the outside world through a circular horizon. If the fish is $\sqrt{7}m$ below the surface of water, then the radius of the circular horizon will be

1. $1m$
2. $2m$
3. $3m$
4. $4m$

Q. A fish looking up through the water sees the outside world containing in a circular horizon. If the fish is 28 cm below the water surface, the radius of that circle is $(R.Iofwater=\frac{4}{3})$

1. 12 cm
2. 14 cm
3. $12\sqrt{7}cm$
4. $28\sqrt{7}cm$

Q. For the given incident ray as shown in figure, for the condition of total internal reflection of this ray, the minimum refractive index of prism will be:-

1. $\frac{\sqrt{3}+1}{2}$
2. $\frac{\sqrt{2}+1}{2}$
3. $\sqrt{\frac{3}{2}}$
4. $\sqrt{\frac{7}{6}}$

Q. In the figure shown, for an angle of incidence 45^{\circ}at the top surface, what is the minimum refractive index needed for total internal reflection at vertical face

1. $\frac{\sqrt{2}+1}{2}$
2. $\sqrt{\frac{3}{2}}$
3. $\sqrt{\frac{1}{2}}$
4. $\sqrt{2}+1$

Q. Critical angle of glass is ${\theta }_1$ and that of water is ${\theta }_2$. The critical angle for water and glass surface would be $({\mu }_g=\frac{3}{2},{\mu }_w=\frac{4}{3})$

1. Less than ${\theta }_2$
2. Between ${\theta }_{1}and{\theta }_2$
3. Greater than ${\theta }_2$
4. Less than ${\theta }_1$