Tag: physics

Questions Related to physics

Which one of waves cannot be seen through electromagnetic spectrum?

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

  1. radio waves

  2. micro waves.

  3. infrared waves.

  4. ultraviolet waves.

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Correct Option: D
Explanation:
Red, blue, green, yellow, orange colors are all part of electromagnetic spectrum that are visible to human eye.
The part which is not visible are UV, X-RAY, GAMMA RAY which have lower wavelength than visible light and infrared, radio waves have higher wavelength than visible.

To distinguish between real gems and artificial gems a merchant may use which of the following radiations?

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

  1. Infrared rays

  2. $\gamma$-rays

  3. X-rays

  4. Ultraviolet rays

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Correct Option: A
Explanation:

To distinguish between real gems and artificial gems a merchant may use infrared radiations. A number of synthetic gems can be distinguished from their natural counterparts by differences in their infrared spectra.  

Maximum diffraction takes place in a given slit for

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

  1. $\gamma $-rays

  2. Ultraviolet light

  3. Infrared light

  4. Radio waves

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Correct Option: D
Explanation:
When the gap size is larger than the wavelength, the wave passes through the gap and does not spread out much on the other side. When the gap size is equal to the wavelength, maximum diffraction occurs. So among all of them radio waves have minimum wavelength and hence it will give maximum diffraction. 

The frequencies of X-rays, $\gamma-rays$ and ultra violet rays are respectively $p, q$ and $r$, then

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

  1. $p > q, q > r$

  2. $p < q, q > r$

  3. $p < q, q < r$

  4. $p > q, q < r$

Show answer
Correct Option: B
Explanation:

Increasing order of wavelengths as given below
$\gamma-rays < X-rays >$ ultravoilet rays
Frequency order
$\gamma-ray > X-rays >$ ultravoilet rays
$\Rightarrow q > p > r$
Thus, $q > p$
$q > r$
$p > r$.

Velocity of x-ray is

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

  1. $3 \times 10^6 m/sec$

  2. $3 \times 10^8 m/sec$

  3. $3 \times 10^5 m/sec$

  4. $3 \times 10^9 m/sec$

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Correct Option: B

Wave length of X-rays is

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

  1. A to 10 A

  2. 10 A to 20 A

  3. 0.001 A to 1 A

  4. 0.1 A to 1 A

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Correct Option: C

What name is given to the type of astronomy having the following characteristics.
I. It is carried out in the waveband $300$nm to $10$nm.
II. The atmosphere is opaque to the incoming radiation from space
III. Observations are to be carried out from above the earth's atmosphere.

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

  1. X-ray astronomy

  2. Ultra-violet astronomy

  3. Infra-red astronomy

  4. Gamma ray astronomy

Show answer
Correct Option: B
Explanation:
Ultra-violet astronomy is carried out in waveband of $10nm-300nm$ in which is above earth's atmosphere.

A beam of ultraviolet light of all wavelengths passes through hydrogen gas at room temperature, in the $x-$direction. Assume that all photons emitted due to electron transitions inside the gas emerge in the $y-$direction. Let $A$ and $B$ denote the lights emerging from the gas in the $x-$ and $y-$directions respectively. Then,

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

  1. some of the incident wavelengths will be absent in $A$

  2. only those wavelengths will be present in $B$ which are absent in $A$

  3. $B$ will contain some visible light

  4. $B$ will contain some infrared light

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Correct Option: A,C,D
Explanation:

$A, C, D$

The magnetic field in a plane electromagnetic wave is given by $=2\times10^{-7} \sin(0.5\times 10^3 x+1.5\times10^{11}t)$. This electromagnetic wave is

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

  1. Visible light

  2. Infrared

  3. Microwave

  4. Radiowave

Show answer
Correct Option: C
Explanation:

The magnetic field in a plane of electromagnetic  wave is given by

$B=2\times 10^{-7}sin(0.5\times 10^3x+1.5\times 10^{11}t)$
from the above, $K=0.5\times 10^3=$ propagation constant
$K=\dfrac{2\pi}{\lambda}$ where, $\lambda=$ wavelength of wave
$\lambda=\dfrac{2\times 3.14}{0.3\times 10^3}$
$\lambda=1.256\times 10^{-2}m$
$\lambda=1.256 cm$
The electromagnetic wave is Microwave radiation in spectrum.

In the EM wave , the amplitude of magnetic field $ H _o $ and the amplitude of electric field $ E _o $ at a place D are related as:

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

  1. $ H _o = E _o $

  2. $ H _ o=\frac { E _ o }{ c } $

  3. $ H _ o=\quad E _ o\quad \sqrt { \frac { \mu _ o }{ \varepsilon _ o } } $

  4. $ H _ o=\quad E _ o\quad \sqrt { \frac { \varepsilon _ o }{ \mu _ o } } $

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Correct Option: D