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Questions Related to physics

Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

According to Maxwell's equation, the velocity of light in any medium is expressed as

  1. $\displaystyle\frac{1}{\sqrt{\mu _0\varepsilon _o}}$

  2. $\displaystyle\frac{1}{\sqrt{\mu\varepsilon}}$

  3. $\displaystyle\sqrt{\frac{\mu}{\varepsilon}}$

  4. $\displaystyle\sqrt{\frac{\mu _0}{\varepsilon}}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Velocity of light in a medium,

$\displaystyle c=\frac{1}{\sqrt{\mu _0\varepsilon _o\mu _r\varepsilon _r}}=\frac{1}{\sqrt{\mu\varepsilon}}$

Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

Maxwell's equation describe the fundamental laws of

  1. electricity

  2. magnetism

  3. mechanics

  4. both (A) and (B)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Maxwell's equation describe the fundamental laws of electricity and magnetism. His equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents.

Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

According to Maxwell's hypothesis, a changing electric field gives rise to

  1. an electromagnetic force

  2. electric displacement current

  3. magnetic field

  4. pressure gradient
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$Answer:-$ C option
$\nabla \times B={ \mu  } _{ 0 }(J+{ \epsilon  } _{ 0 }\dfrac { dE }{ dt } )$
using this equation of maxwell we can say changing electric field $\dfrac{dE}{dt}$ induces magnetic field.
Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

The electric field associated with an e.m. wave in vacuum is given by $\vec {E} = 40\cos (kz - 6\times 10^{8}t)\hat {i}$, where $E, z$ and $t$ in $volt/m$, meter and seconds respectively. The value of wave vector $k$ is

  1. $6m^{-1}$

  2. $3m^{-1}$

  3. $2m^{-1}$

  4. $0.5m^{-1}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Given: The electric field associated with  an electromagnetic wave in vacuum is given by $\vec E =40 \cos(kz−6\times 10^8t)\hat i$  , where E, z and t are in volt per meter, meter and second respectively.
To find the value of wave vector k
Solution: 
We know electromagnetic wave eqution is
$E=E _0\cos(kz-\omega t)$
And given equation is
$\vec E =40 \cos(kz−6\times 10^8t)\hat i$
By comparing these two, we get
$\omega=6\times10^8$ and 
$E _0=40\hat i$
we also know,
Speed of electromagnetic wave, $v=\dfrac \omega k$
where v is the speed of the light
Hence, $k=\dfrac \omega v\\\implies k=\dfrac {6\times 10^8}{3\times 10^8}\\\implies k=2m^{-1}$
is the required value
Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

Wavelength of light in different media are proportional to:

  1. speed of light in that medium

  2. Amplitude of light in that medium

  3. frequency of light in that mrdium

  4. Nove of above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The speed of light in a medium is given by v = f * lambda. Since frequency (f) remains constant when light moves between media, the wavelength (lambda) is directly proportional to the speed of light (v) in that medium.

Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

The Maxwell's equation : $\oint \vec { \mathrm { B } }$ . $\vec { \mathrm { d } 1 } = \mu _ { 0 } \left( \mathrm { i } + \varepsilon _ { 0 } \cdot \frac { \mathrm { d } \phi _ { \mathrm { E } } } { \mathrm { dt } } \right)$ is a statement of

  1. Faraday's law of induction

  2. Modified Ampere's law

  3. Gauss's law of electricity

  4. Gauss's law of magnetism
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

In Maxwell's velocity distribution curve area under the graph 

  1. Increases when temperature is increased

  2. Deccreases when temperature is increased

  3. Remains same at all temperature

  4. Depends on the pressure of the gas
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Area under the Maxwell's velocity distribution curve gives the number of particles. Since number of particles remains the same at all the temperatures, so the area under the curve also remains the same at all temperature.

Multiple choice physics option a: relativity maxwell's equations the nature of light introduction to electromagnetic waves

According to the electromagnetic wave theory, light consists of electric and magnetic fields which are __________.

  1. parallel to each other

  2. perpendicular to each other

  3. inclined at an angle of ${45}^{o}$ to each other

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Light consists of electric and magnetic field that are perpendicular ${ 90 }^{ 0 }$ to each other.
APPOACH by example
Electric field inside plates. The magnetic field this given rise to via the displacement current is along the perimeter of the circle parallel to capauatates plates.

So B and E are perpendicular in this case.