Tag: electromagnetic waves

Questions Related to electromagnetic waves

State whether true or false :

Ultraviolet rays are used to take photographs in darkness.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Wrong

Infrared is used in dark for photography. All body emit infrared radiation every time.
Since infrared radiation is invisible, photography in total darkness can be readily carried out if infrared film is used and the light source is covered with a light-absorbing but infrared-transmitting filter.

The part of the electromagnetic spectrum which is suitable for radar systems used in aircraft navigation :

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

  1. X-Rays

  2. Gamma Rays

  3. Microwaves or short radiowaves 

  4. Ultraviolet

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Correct Option: C
Explanation:

Microwaves or short radiowaves are suitable for radar systems used in aircraft navigation because of their short wavelengths.

 Which one of waves tans our skin and causes some substances to become fluorescent?

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

  1. infrared waves.

  2. ultraviolet waves.

  3. gamma rays.

  4. infrared and ultraviolet waves both.

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Correct Option: B
Explanation:

Ultraviolet rays (or waves) tan our skin and cause some substances to become fluoroseun sun is important source of ultraviolet light. Sun rays reach our skin and burns the upper layer of skin, causing sunburns prolonged doses of UV radiation can induce skin cancer in human beings.

Ozone layer is protecting us from UV rays but the problem is that Ozone layer is also depleting because of excessive use of CFC's.

In photocell cesium, coated oxidized silver cathode emits electrons for

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

  1. visible light.

  2. ultraviolet.

  3. infrared light.

  4. x-rays.

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Correct Option: C
Explanation:

In photocell cesium, coated oxidised silver cathode emits electrons for infrared light.

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. $p > q, q < r$

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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