Tag: electromagnetic waves

Questions Related to electromagnetic waves

The matter-wave picture of electromagnetic wave/radiation elegantly incorporated the:

electromagnetic spectrum electromagnetic waves physics

  1. Heinsenbergs uncertainty principle

  2. correspondence principle

  3. cosmic theory

  4. Hertzs observations

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Correct Option: A
Explanation:

The matter-wave picture of electromagnetic wave/radiation elegantly incorporated  the Heisenberg uncertainty principle.

The correct option is A.

If $c$ is the speed, $\nu$ is frequency and $\displaystyle \lambda $ is wavelength of EM waves, then

electromagnetic spectrum electromagnetic waves physics

  1. $\displaystyle c=\nu\lambda $

  2. $\displaystyle \frac { \lambda }{ \nu } =c$

  3. $\displaystyle \frac { \nu }{ \lambda } =c$

  4. $\displaystyle \frac { 1 }{ \lambda } =\frac { c }{ \nu} $

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Correct Option: A
Explanation:

$\displaystyle c=\nu \lambda $
$c=$speed
$\nu=$Frequency
$\displaystyle \lambda $ = wavelength

The broad wavelength range of visible spectrum is:

electromagnetic spectrum electromagnetic waves physics

  1. $4000-8000A^o$

  2. $2000-4000A^o$

  3. $10000-20000A^o$

  4. None of the above

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Correct Option: A
Explanation:

The wavelength range of $4000-8000 A^o$ is known as visible spectrum as waves within this wavelength range create a sensation of vision in our eyes.

Identify which of the following light rays has the highest energy?

electromagnetic spectrum electromagnetic waves physics

  1. Violet

  2. Green

  3. Yellow

  4. Orange

  5. Red

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Correct Option: A
Explanation:

Energy of light ray      $E = h\nu$                $\implies E \propto \nu$

Among all the visible rays, violet ray has the highest frequency, Thus violet ray has the highest energy. 

The portion of the spectrum beyond the red end is called

electromagnetic spectrum electromagnetic waves physics

  1. UV spectrum

  2. Infrard spectrum

  3. Microwave

  4. All

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Correct Option: B
Explanation:

The portion of spectrum just beyond the red end is called infrared spectrum, while the portion of the spectrum just before the voilet end is called the ultravoilet spectrum.

Wavelength of gamma rays are :

electromagnetic spectrum electromagnetic waves physics

  1. ${ 10 }^{ -10 }m$ to less than ${ 10 }^{ -14 }m$

  2. ${ 10 }^{ -14 }m$ to less than ${ 10 }^{ -10 }m$

  3. ${ 10 }^{ -11 }m$ to less than ${ 10 }^{ -14 }m$

  4. ${ 10 }^{ -14 }m$ to less than ${ 10 }^{ -6 }m$

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Correct Option: A
Explanation:

Electromagnetic radiations are present all around us in different forms such as microwaves, radio waves, gamma rays, and X-rays. These radiations can be defined as a form of energy produced by the movement of electrically charged particles that can be found in matter or vacuum or by oscillating magnetic or electric disturbance.


Properties of electromagnetic radiations :

1) They travel through empty space
2) The speed of light always remains constant i.e. 2.99792458 X 10 8 m/s.
3) Wavelength is the measure between the distance of either troughs or crests.  Its symbol is 'Lambda'.

Gamma rays have no mass.  They arise from the high-frequency end of the electromagnetic spectrum.  They have the highest penetration power.   They are at least ionizing.  The Gamma rays carry a large amount of energy and can travel through the thick and thin material. Gamma rays have frequencies greater than about 1018 cycles per second or Hertz.  They have wavelengths of less than 100 picometer.  Gamma rays can kill living cells.  It is used to kill cancerous cells.   They can also kill bacteria.

Electromagnetic wave with frequencies greater than the critical frequency of ionosphere cannot be used for communication using sky wave propagation because

electromagnetic spectrum electromagnetic waves physics

  1. The refractive index of ionosphere becomes very high for $f > f _ { c }$

  2. The refractive index of ionosphere becomes very low for $f > f _ { c }$

  3. The refractive index of ionosphere becomes very high for $f < f _ { c }$

  4. The refractive index of ionosphere becomes very low for $f < f _ { c }$

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Correct Option: B

Which is having minimum wavelength ?

electromagnetic spectrum electromagnetic waves physics

  1. X-rays

  2. Ultraviolet rays

  3. y - rays

  4. Cosmic rays

Show answer
Correct Option: D
Explanation:

Cosmic Rays             ${{10}^{-14}}m\,\,\,to\,\,{{10}^{-12}}m$

$\gamma $ Rays                        ${{10}^{-12}}m\,\,\,to\,\,{{10}^{-10}}m$

$x$ Rays                        ${{10}^{-10}}m\,\,\,to\,\,{{10}^{-09}}m$

Ultraviolet Rays         ${{10}^{-07}}m\,\,\,to\,\,\,4\times {{10}^{-07}}m$ 

Hence, Cosmic Rays have smallest wavelength.

If $P$ represents radiation pressure, $c$ represents speed of lights and $l$ represents radiation energy striking a unit area per second, then non -zero integers $x,y$ and $z$ such that $P^ xl^ yc^z$ is dimensionless are

electromagnetic spectrum electromagnetic waves physics

  1. $x=0, y=0, z=0$

  2. $x=1, y=-1, z=1$

  3. $x=-1, y=1, z=1$

  4. $x=1, y=1, z=1$

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Correct Option: A

An electromagnetic radiation has an energy 14.4 eV. To which region of electromagnetic spectrum does it belong?

electromagnetic spectrum electromagnetic waves physics

  1. Ultraviolet region

  2. Visible region

  3. X-ray region

  4. Y-ray region

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Correct Option: C
Explanation:

$ E=\dfrac{hc}{\lambda } $

$ \lambda =\dfrac{hc}{E}=\dfrac{6.626\times {{10}^{-34}}\times 3\times {{10}^{8}}}{14.4\times 1.6\times {{10}^{-19}}}=0.86\times {{10}^{-09}} $

Cosmic Rays                ${{10}^{-14}}m\,\,\,to\,\,{{10}^{-12}}m$

$\gamma$ Rays                        ${{10}^{-12}}m\,\,\,to\,\,{{10}^{-10}}m$

$x$ Rays                        ${{10}^{-10}}m\,\,\,to\,\,{{10}^{-09}}m$

Ultraviolet Rays         ${{10}^{-7}}m\,\,\,to\,\,\,4\times {{10}^{-7}}m$

Hence, it lies in $x$ Rays region.