Tag: physics

Questions Related to physics

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

Show answer
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

Show answer
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.

Electromagnetic wave of intensity $1400\ W/m^{2}$ falls on metal surface on area $1.5\ m^{2}$ is completely absorbed by it. Find out force exerted by beam.

electromagnetic spectrum electromagnetic waves physics

  1. $14\times 10^{-5}N$

  2. $14\times 10^{-6}N$

  3. $7\times 10^{-5}N$

  4. $7\times 10^{-6}N$

Show answer
Correct Option: D
Explanation:
For a perfectly absorbing surface,
$F=\dfrac{IA}{C}$

$=\dfrac{(1400w/m^2\times 1.5m^2)}{(3\times 10^8m/s)}$

$=7\times 10^{-6}N$.

Which one of the following is the primary effect of UV radiation caused due to depletion of ozone layer?

electromagnetic spectrum electromagnetic waves physics

  1. Heart attack

  2. Skin cancer

  3. High fever

  4. All of these

  5. None of these

Show answer
Correct Option: B
Explanation:

The ozone layer prevents most harmful UV wavelengths of ultraviolet light (UV light) from passing through the Earth's atmosphere. These wavelengths cause skin cancer, sunburn and cataracts, which were projected to increase dramatically as a result of thinning ozone, as well as harming plants and animals.

A gas of identical hydrogen like atoms has some atoms in ground state and some atoms in a particular excited state and there are no atoms in any other energy level. The atoms of the gas make transition to a higher state by absorbing monochromatic light of wavelength $304 \AA $. subsequently, the atoms emit radiation of only six different photon energies. Some of emitted photons have wavelength $304 \AA $, some have wavelength more and some have less than $304 \AA $ ( Take $hc = 12420 eV - \AA $)
Find the principal quantum number of the initially excited state.

electromagnetic spectrum electromagnetic waves physics

  1. 1

  2. 2

  3. 3

  4. 4

Show answer
Correct Option: A

A gas of identical hydrogen like atoms has some atoms in ground state and some atoms in a particular excited state and there are no atoms in any other energy level. The atoms of the gas make transition to a higher state by absorbing monochromatic light of wavelength $304 \mathring A $. subsequently, the atoms emit radiation of only six different photon energies. Some of emitted photons have wavelength $304 \mathring A $, some have wavelength more and some have less than $304 \mathring A $ ( Take $hc = 12420 eV - \mathring A $). Find the principal quantum number of the initially excited state.

electromagnetic spectrum electromagnetic waves physics

  1. 1

  2. 2

  3. 3

  4. 4

Show answer
Correct Option: A

A gas of identical hydrogen like atoms has some atoms in ground state and some atoms in a particular excited state and there are no atoms in any other energy level. The atoms of the gas make transition to a higher state by absorbing monochromatic light of wavelength $304 \mathring A $. subsequently, the atoms emit radiation of only six different photon energies. Some of emitted photons have wavelength $304 \mathring A $, some have wavelength more and some have less than $304 \mathring A $ ( Take $hc = 12420 eV - mathring A $). Find the principal quantum number of the initially excited state.

electromagnetic spectrum electromagnetic waves physics

  1. 1

  2. 2

  3. 3

  4. 4

Show answer
Correct Option: A

Mark the correct option in impure spectrum :

electromagnetic spectrum electromagnetic waves physics

  1. Order of colours is reverse

  2. Order of colours is irregular

  3. colours are overlapped

  4. no colours is present

Show answer
Correct Option: C
Explanation:

For impure spectrum:

  1. The order of colours is are straight, hence option a is false
  2. Order of colours are regular
  3. Colours are overlapped each other in impure spectrum
  4. Colours are present in impure spectrum
Hence option C is the correct statement according to the impure spectrum

Radiations of intensity 0.5 W/m2 are striking a metal plate. The pressure on the plate is

electromagnetic spectrum electromagnetic waves physics

  1. $0.166 \times 10^{-8} N/m2$

  2. $0.332 \times 10-8 N/m^2$

  3. $0.111 \times 10-8 N/m^2$

  4. $0.083 \times 10-8 N/m^2$

Show answer
Correct Option: A
Explanation:

Intensity or power per unit area of the radiations,
$P = pv$
$\Rightarrow p=\dfrac{p}{v} = \dfrac{0.5}{3\times 10^8}=0.166\times 10^{-8}N/m^2$