Tag: physics

Questions Related to physics

A plane electromagnetic wave of frequency $40 MHz$ travels in free space in the X-direction. At some point and at some instant, the electric field $\vec{E}$ has its maximum value of $750N/C$ in Y-direction. The wavelength of the wave is-

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. 3.5 m

  2. 5.5 m

  3. 7.5 m

  4. 9.5 m

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Correct Option: A

Find the distance (in meters) traveled by a radio wave in $5.00$ seconds?

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. $3\times {10}^{9}m$

  2. $2.9\times {10}^{9}m$

  3. $3.6\times {10}^{6}m$

  4. $1.5\times {10}^{9}m$

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Correct Option: A

The infra-red spectrum lies between:

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. radio wave and micro-wave region

  2. the micro-wave and visible region

  3. the visible and ultra violet region

  4. the ultra violet and the X-ray region

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Correct Option: B
Explanation:
                        Light comparison
Name            wavelength                   Frequency
visible          $400nm-700nm$        $790THz-430THz$
Infrared        $700nm-1mm$           $430THz-300GHz$
Microwave   $1mm-1$meter           $300GHz-300MHz$
Therefore the infrared spectrum lies between (B), the micro-wave & visible region.

X - ray beam can be deflected by 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. Magnetic field

  2. Electric field

  3. Both (a) & (b)

  4. None of these

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Correct Option: D
Explanation:

$X-$rays aren't deflected by electrons and magnetic fields because $x-$rays do not carry and charge. They are electro-magnetic radiations and therefore cannot be deflected by electronic or any magnetic fields.

Assertion :- Microwave communication is preferred over optical communication. 
Reason :- Microwaves provide large number of channels and band width compared to optical signals. 

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. Both assertion and reason are true and the reason is correct explanation of assertion.

  2. Both assertion and reason are true and the reason is not the correct explanation of assertion.

  3. Assertion is true but reason is false.

  4.  Both assertion and reason are false.

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Correct Option: D
Explanation:

Both assertion and reason are false.

Optical communication is always preferred over microwave

communication also Bandwidth and number of channels are more in case of optical communication.

Hence both statements are false.
so the  correct option is D,

_____ light creates intense heating when it is incident on a substance

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. visible

  2. ultra violet

  3. Infra red

  4. X-ray

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Correct Option: C

The structure of solids is studied by

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. X-rays

  2. $\gamma-rays$

  3. Cosmic rays

  4. Infrared rays

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Correct Option: A

If a source of power $4\ kW$ produces $10^{20}$ photons/second, the radiation belongs to a part of the spectrum called:-

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. $\gamma$-rays

  2. $X$-rays

  3. Ultraviolet rays

  4. Microwave

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Correct Option: B
Explanation:

$4\times { 10 }^{ 3 }={ 10 }^{ 20 }\times h\nu$ 

where $\nu=$frequency
$\nu =\cfrac { 4\times { 10 }^{ 3 } }{ { 10 }^{ 20 }\times 6.023\times { 10 }^{ -34 } } $
$\nu =6.64\times { 10 }^{ 16 }Hz$
This frequency lies in the spectrum of X-rays.

When accelerating voltage is increased from $10\ kV$ to $20\ kV$ in an X-ray tube, the gap between the wavelengths of $K _{\alpha}$ line and lowest end of continuous spectrum increases three times. The atomic number of the target element is:-

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. $29$

  2. $27$

  3. $25$

  4. $23$

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Correct Option: A

The radio waves of frequency 30 MHz to 300 MHz belong to:

physics electromagnetic waves properties and uses of different radiation electromagnetic spectrum spectrum

  1. high frequency band

  2. very high frequency band

  3. ultra high frequency band

  4. super high frequency band.

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Correct Option: B