Reflection of Light

Q. Find the angle of incidence so that the incident light ray retraces its path after third reflection.

1. ${45}^{\circ }$
2. ${75}^{\circ }$
3. ${60}^{\circ }$
4. ${70}^{\circ }$

Q. A mirror is inclined at an angle $\theta$ with the horizontal and a ray of light is incident on it as shown. Find the angle made by the reflected ray with the horizontal.

1. $\theta$
2. $2\theta$
3. $\theta /2$
4. Zero

Q. A ray of light is incident on a plane mirror along a vector $(\hat{i}+\hat{j}-\hat{k})$. The normal on the incident point is along $\left(\hat{k}\right)$. The unit vector along the reflected ray will be:

1. $\frac{1}{\sqrt{2}}(\hat{i}+\hat{j}-\hat{k})$
2. $\frac{-1}{\sqrt{3}}(\hat{i}+\hat{j}+\hat{k})$
3. $-\hat{i}-\hat{j}$
4. $\frac{1}{\sqrt{3}}(\hat{i}+\hat{j}+\hat{k})$

Q. When a wave undergoes reflection in a denser medium then its phase changes by?

Q. A ray of light falls on a plane mirror. When the mirror is turned clockwise about an axis along the plane of the mirror by ${20}^{\circ }$, the incident ray gets deflected by ${45}^{\circ }$. The original incidence angle is

1. ${80.5}^{\circ }$
2. ${65.5}^{\circ }$
3. ${45.5}^{\circ }$
4. ${87.5}^{\circ }$

Q. Two plane mirrors are inclined at an angle $\theta$ as shown in the figure. Find the value of $\theta$ such that the light ray retraces its path after second reflection.

1. ${60}^{\circ }$
2. ${30}^{\circ }$
3. ${45}^{\circ }$
4. ${75}^{\circ }$

Q. When the angle of incidence on a material is ${60}^{\circ }$, the reflected light is completely polarized. The velocity of the refracted ray inside the material is $(\text{in m/s}$)

1. $3\times {10}^8$
2. $\frac{3}{\sqrt{2}}\times {10}^8$
3. $\sqrt{3}\times {10}^8$
4. $0.5\times {10}^8$

Q. Two polaroid sheets are placed one over the other with their axes inclined to each other at an angle $\theta$. If only $12.5$% of intensity of unpolarised light incident on the first sheet emerges out from the second sheet, the value of $\theta$ is

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

Q. A ray of light is approaching a set of three mirrors as shown in the diagram. The light ray is approaching the first mirror at an angle of ${45}^{\circ }$ with the mirror surface. How many times will the ray reflect before it exits the system?

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

Q. The figure shows a ray incident at incidence angle ($i$) $\pi /3$. The plot drawn shows the variation of $|r-i|$ versus $({\mu }_1/{\mu }_2=k$), where $r$ = angle of refraction.
The ray is going from ${\mu }_2$ to ${\mu }_1$. Choose possible correct options.

1. $K_1=\frac{2}{\sqrt{3}}$
2. ${\theta }_1=\frac{\pi }{6}$
3. $K_2=1$
4. ${\theta }_2=\frac{\pi }{3}$

Q. A light ray parallel to the $x-$axis strikes the outer reflecting surface of a sphere at a point $(2,2,0)$. Its centre is at the point $(0,0,–1)$. The unit vector along the direction of the reflected ray is $x\hat{i}+y\hat{j}+z\hat{k}$. Find the value of $\frac{yz}{x^2}$.

Q. Two plane mirrors are inclined at angle $\theta$ as shown in figure. If a ray parallel to $OB$ strikes the other mirror at $P$ and finally emerges parallel to $OA$ after two reflections, then $\theta$ is equal to

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

Q.

A thick plane mirror shows a number of images of the filament of an electric bulb. Of these, the brightest image is the

1. First

2. Fourth

3. Second

4. Last

Q.

When light wave suffers reflection at the interface from air to glass, the

change in phase of the reflected wave is equal to

[CPMT 1991; J & KCET 2004]

1. 0

2. 

3. 

4. 

Q. If the incident ray is rotated by an angle of ${30}^{\circ }$ while the plane mirror is at rest, the reflected ray gets rotated by .

1. ${30}^{\circ }$
2. ${90}^{\circ }$
3. $0^{\circ }$
4. ${60}^{\circ }$

Q. ${\hat{n}}_1$ is the unit vector along incident ray, ${\hat{n}}_2$ along the normal to plane mirror and $\widehat{n_3}$ is the unit vector along reflected ray direction, then which of the following must be true?

1. ${\hat{n}}_1.{\hat{n}}_3=0$
2. ${\hat{n}}_1.{\hat{n}}_2=0$
3. $({\hat{n}}_1\times {\hat{n}}_2).{\hat{n}}_3=0$
4. $({\hat{n}}_1\times {\hat{n}}_2)\times {\hat{n}}_3=0$

Q. When the angle of incidence is ${60}^{\circ }$ on the surface of a glass slab, it is found that the reflected ray is completely polarized. The velocity of light in glass is,

1. $\sqrt{2}\times {10}^8{\text{ms}}^{-1}$
2. $\sqrt{3}\times {10}^8{\text{ms}}^{-1}$
3. $2\times {10}^8{\text{ms}}^{-1}$
4. $3\times {10}^8{\text{ms}}^{-1}$

Q. When the angle of incidence on a material is ${60}^{\circ }$, the reflected light is completely polarized. The velocity of the refracted ray inside the material is $\left({\text{in ms}}^{-1}\right)$

1. $3\times {10}^8$
2. $\left(\frac{3}{\sqrt{2}}\right)\times {10}^8$
3. $\sqrt{3}\times {10}^8$
4. $0.5\times {10}^8$
   

Q. The phase change in reflected wave, when light wave suffers reflection at the interface from air to glass is

1. $0$
2. $\frac{\pi }{2}$
3. $\pi$
4. $2\pi$

Q. A ray of light falls on a plane mirror. When the mirror is turned clockwise about an axis along the plane of the mirror by ${20}^{\circ }$, the incident ray gets deflected by ${45}^{\circ }$. The original incidence angle is

1. ${80.5}^{\circ }$
2. ${65.5}^{\circ }$
3. ${45.5}^{\circ }$
4. ${87.5}^{\circ }$

Q. If the incident ray is stationary, but the plane mirror rotates by an angle of ${30}^{\circ }$, then the reflected ray gets rotated by .

1. ${60}^{\circ }$
2. ${30}^{\circ }$
3. ${90}^{\circ }$
4. $0^{\circ }$

Q. If the incident ray given by vector $\overrightarrow{a}=\hat{i}-\hat{j}$, is incident on a plane mirror having its normal along $\hat{j}$, then the unit vector along the reflected ray is given by :

1. $\frac{\hat{i}+\hat{j}}{\sqrt{3}}$
2. $\frac{\hat{i}+\hat{j}}{\sqrt{2}}$
3. $\hat{i}+\hat{j}$
4. $\frac{\hat{i}-\hat{j}}{\sqrt{2}}$

Q. Two plane mirrors each $14\text{m}$ long are facing each other as shown in the figure. The distance between the mirrors is $\sqrt{3}\text{m}$. A light ray is incident at the corner end of one of the mirrors at an angle of incidence ${30}^{\circ }$. How many times does the ray gets reflected before it reaches the other corner end of the either mirrors?

1. $14$
2. $10$
3. $12$
4. $18$

Q. For a given medium, the polarizing angle is ${60}^{\circ }$. The critical angle for this medium is
$\left({\sin }^{-1}\right(0.5773)={35}^{\circ }{16}^{\prime }\text{and}{\sin }^{-1}(0.886)={60}^{\circ })$

1. ${60}^{\circ }$
2. ${35}^{\circ }{16}^{\prime }$
3. ${30}^{\circ }$
4. ${45}^{\circ }{30}^{\prime }$

Q. Two plane mirrors are inclined to each other at an angle ${60}^{\circ }.$ If a ray of light incident on the first mirror is parallel to the second mirror, it is reflected from the second mirror

1. Perpendicular to the first mirror
2. Parallel to the first mirror
3. Parallel to the second mirror
4. Perpendicular to the second mirror

Q.

A plane mirror reflects a pencil of light to form a real image. Then the pencil of light incident on the mirror is
[MP PMT 1997; DCE 2001, 03]

1. Parallel

2. Convergent

3. Divergent

4. None of the above

Q. coherent light sources can only be obtained by the method of division of wavefront. why this statement is false??

Q.

A ray of light is incidenting normally on a plane mirror. The angle of reflection will be

Q. When a plane mirror is rotated through an angle $\theta$, the reflected ray turns through the angle $2\theta$, then size of the image:

1. Is doubled
2. Is halved
3. Remains the same
4. Becomes infinite

Q. A ray of light is incident on a plane mirror along a vector $(\hat{i}+\hat{j}-\hat{k}).$ The normal on incident point is along $(\hat{i}+\hat{j}).$ The unit vector along the reflected ray is

1. $\frac{1}{\sqrt{3}}(\hat{i}+\hat{j}+\hat{k})$
2. $-\frac{1}{\sqrt{3}}(\hat{i}+\hat{j}+\hat{k})$
3. $\frac{1}{\sqrt{3}}(-\hat{i}-\hat{j}+\hat{k})$
4. $\frac{(\hat{i}-\hat{j}-\hat{k})}{\sqrt{3}}$