Tag: principle of reversibility of path of light

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Questions Related to principle of reversibility of path of light

Multiple choice physics light : reflection and refraction from plane surface introduction to light and mirror magic with mirrors image formation by plane mirror principle of reversibility of path of light refractive index

A ray of light making an angle $10^o$ with the horizontal is incident on a plane mirror making angle $\theta$ with the horizontal. What should be the value of $\theta$ so that the reflected ray goes vertically upward?

  1. $30^o$

  2. $40^o$

  3. $50^o$

  4. $60^o$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The situation is as shown in figure:
The reflected ray makes an angle, $100-\theta$ with the normal. This is also equal to $\theta$.
$\therefore 100-\theta=\theta$
$\Rightarrow \theta=50^o$
Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

If refraction index of glass with respect to air is $ _{a}{u} _{g} = \dfrac{3}{2}$, the refraction index of air with respect to glass will be $ _{g}{u} _{a} =$

  1. ${3}/{2}$

  2. ${2}/{3}$

  3. ${1}/{3}$

  4. ${1}/{2}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
refractive index of glass w.r.t air =${ _{ a }{ \mu  } _{ g }= }\dfrac { 3 }{ 2 } $
then,
refractive index of air w.r.t glass  =$ _{ g }{ \mu  } _{ a }=\dfrac { 1 }{ _{ a }{ \mu  } _{ g } } $

$ _{ g }{ \mu  } _{ a }=\dfrac { 1 }{ _{ a }{ \mu  } _{ g } } =\dfrac { 2 }{ 3 } $
Option B is correct.
Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

The refractive index of water with respect to air is $ _{a}{u} _{w}$ and of glass with respect to air is $ _{a}{u} _{g}$. Express the refractive index of glass with respect to water

  1. $\dfrac{ _{a}{u} _{g}}{ _{a}{u} _{w}}$

  2. $\dfrac{ _{g}{u} _{a}}{ _{a}{u} _{w}}$

  3. $\dfrac{ _{a}{u} _{w}}{ _{a}{u} _{g}}$

  4. $\dfrac{ _{a}{u} _{a}}{ _{g}{u} _{g}}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Refractive index of water w.r.t air
$ _{a}\mu _{w}=\dfrac{\mu _{w}}{\mu _{a}}$
Refractive index of glass w.r.t air
$ _{a}\mu _{g}=\dfrac{\mu _{g}}{\mu _{a}}$
Hence refractive index of glass w.r.t water
$ _{w}\mu _{g}=\dfrac{\mu _{g}}{\mu _{w}}   =\dfrac{ _{a}\mu _{g}}{ _{a}\mu _{w}}$

Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

At ray of light is incident in medium 1 at an angle of $37^{o}$ and gets refracted in medium 2 at an angle of $53^{o}$. What will be angle of refraction if light is incident in medium 2 at an angle of $53^{o}$.

  1. $37^{o}$

  2. $53^{o}$

  3. $36^{o}$

  4. $45^{o}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Principle of reversibility states that when final path of a ray of light after any number of reflections and refractions is reversed, the ray retraces its entire path or in simple words, light follows exactly the same path if its path of travel is reversed.

Thus angle of refraction of light in medium $1$ will be $37^o$.

Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

When a ray of light enters a medium of refractive index $\mu $ from air. It is observed that the angle of refraction is half the angle of incidence. The angle of incidence is :

  1. $2 cos^{-1}(\frac{\mu }{2})$

  2. $ cos^{-1}(\frac{\mu }{2})$

  3. $2 cos^{-1}(\mu )$

  4. $2 sin^{-1}(\frac{\mu }{2})$
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

Refractive index of diamond with respect to glass is $1.6$ and absolute refractive index of glass is $1.5$. Find out the absolute refractive index of diamond.

  1. $1.06$

  2. $0.93$

  3. $2.4$

  4. $0.75$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Given,

Refractive index of diamond with respect to glass, ${ _{ g }{ n } _{ d } } = 1.6$,

Absolute refractive index of glass, $n _{g} = 1.5$

Refractive index of diamond with respect to glass $= \dfrac {\text {Absolute refractive index of diamond}}{\text {Absolute refractive index of glass}}$

Therefore, absolute refractive index of diamond $=$ Refractive index of diamond with respect to glass $\times$ Absolute refractive index of glass $= 1.6 \times 1.5 = 2.4$
Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

The refractive index of water is $\dfrac{4}{3}$ and of glass is $\dfrac{3}{2}$. What will be the refractive index of glass with respect to water?

  1. $9.1$

  2. $2.623$

  3. $1.125$

  4. $1$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
refractive index of water =${ _{ a }{ \mu  } _{ w }= }\dfrac { 4 }{ 2 } $
refractive index of glass = ${ _{ a }{ \mu  } _{ g }= }\dfrac { 3 }{ 2 } $

then refractive index of glass w.r.t. water is
$ _{ w }{ \mu  } _{ g }= _{ a }{ \mu  } _{ g }\times \dfrac { 1 }{ _{ a }{ \mu  } _{ w } } $
${ _{ w }{ \mu  } _{ g }= _{ a }{ \mu  } _{ g }\times \dfrac { 1 }{ _{ a }{ \mu  } _{ w } } =\dfrac { 3 }{ 2 } \times \dfrac { 3 }{ 4 } =\dfrac { 9 }{ 8 } =1.125 }$

Option C is correct.


Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

In its simplest interpretation the principle of reversibility is a corollary of __________ of the refraction  of light.

  1. Snell's law

  2. Law of refraction

  3. Law of reflection

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Principle of reversibility is a corollary of snells law-

Like with reflection, refraction also involves the angles that the incident ray and the refracted ray make with the normal to the surface at the point of refraction. Unlike reflection, refraction also depends on the media through which the light rays are traveling. This dependence is made explicit in Snell's Law via refractive indices, numbers which are constant for given media1.

Snell's Law is given in the following diagram.

Basic illustration of Snell's Law.

Multiple choice physics light : reflection and refraction from plane surface principle of reversibility of path of light image formation by plane mirror refractive index

Principle of reversibility holds true for

  1. Reflection

  2. Refraction

  3. Reflection and Refraction

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Path of ray of light is reversible or light traces back it's path while traveling in reverse direction or a ray of light can pass in either direction along the same path.
So
Principle of reversibility holds true for both reflection and refraction.