Tag: electromagnetic waves

Questions Related to electromagnetic waves

Identify the most notable difference between a ultraviolet wave and a light wave ?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. Speed

  2. Refractive index

  3. Reflectivity

  4. Amplitude

  5. Frequency

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Correct Option: E
Explanation:

Both , ultraviolet and light wave are electromagnetic waves , having the speed of light , but in electromagnetic frequency spectrum ultraviolet wave falls before light wave , in the decreasing order of frequency.It means frequency of UV waves is greater than light wave.

Electromagnetic waves of wavelength ranging from $100\mathring{A}$ to $\mathring{A}$ comes under 

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. X-rays

  2. UV regions

  3. Visible region

  4. Infrared region

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Correct Option: A
Explanation:
X-rays: $10 nm-10 pm\  i.e.\ 10^{-8}m-10^{-11}m$
Given frequency range: $100 \mathring A-  1 \mathring A\ i.e.\ 10^{-8}m-10^{-10}m$
Hence, given wavelength range falls under X-rays

Which of the following types of waves travels at the greatest speed through the vacuum?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. Radio waves

  2. Microwaves

  3. Ultraviolet light

  4. $X$-rays

  5. None of the above; all these waves would travel at the same speed

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Correct Option: E
Explanation:

Since the speed of any types of wave in vacuum remains constant so all wave travel at the same speed. 

Fill the most suitable option. Mosquitoes and some snakes find their food using vision in the ___ range.

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. infrared

  2. ultraviolet

  3. radio

  4. microwave

  5. visible light

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Correct Option: A
Explanation:

Infrared light has longer wavelengths and lower energy than visible light and cannot be seen with the human eye. Mosquitoes, vampire bats, bed bugs, and some snake and beetle species, however, can use portions of the infrared spectrum for vision. Sometimes humans can “see" infrared energy in the form of heat.

According to the electromagnetic spectrum, radio waves have the ___frequency and the  _______ wavelength.

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. lowest; largest

  2. lowest; smallest

  3. highest; smallest

  4. highest; largest

  5. medium; medium

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Correct Option: A
Explanation:

Radio waves are the least energetic waves among other waves. They have the lowest frequency and thus the largest wavelength. Due to this large wavelength character, the radio waves are used in data transmission purposes, since they are hard to interact with particles in the atmosphere.

According to the electromagnetic spectrum, As the frequencies of the pure spectral colours increase, the wavelengths of the colours:

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. decrease

  2. increase

  3. remain the same

  4. decrease by a factor of 2

  5. increase by a factor of 2

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Correct Option: A
Explanation:

Speed of all the electromagnetic waves is constant and is equal to speed of light  i.e  $c$

Using        $\lambda \times \nu = c = constant$
$\implies$ If frequencies of the pure spectral colours increase then their wavelength will decrease.

According to the electromagnetic spectrum. Which of the following is NOT a pure spectral colour?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. white

  2. violet

  3. red

  4. blue

  5. yellow

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Correct Option: A
Explanation:

Electromagnetic spectrum of visible light :     $VIBGYOR$

VIBGYOR stands for Violet, Indigo, Blue, Green, Yellow, Orange and Red.
These are pure spectral colours but not white. Infact, white colour is formed due to  interference of all these 7 colours.

Which of the following light has the combination of all frequencies of visible light ?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. white light

  2. black light

  3. ultraviolet light

  4. infrared light

  5. transparency

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Correct Option: A
Explanation:

The visible light contains 7 colours  :  Violet, indigo, Blue, Green, Yellow, Orange and Red.

White colour is formed by the interference of all 7 colours, thus white light has the combination of all frequencies of visible light.

Identify which of the following is NOT a source of visible light?

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. red-hot metal

  2. cool metal

  3. fluorescent bulb

  4. the Sun

  5. fire

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Correct Option: B
Explanation:

When the electrons in the atom are excited, for example by being heated, the additional energy pushes the electrons to higher energy orbits. When the electrons fall back down and leave the excited state, energy is re-emitted in the form of a photon.

Thus the hot objects release photons that have energies lying in the visible region. However photons from cool metal do not have energy enough to lie in visible region.

If a particular electromagnetic wave has the highest frequencies among the other electromagnetic waves then it should have the smallest

physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

  1. wavelengths

  2. speeds

  3. amplitudes

  4. energies

  5. periods

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Correct Option: A
Explanation:

Electromagnetic waves travel with constant speed equal to that of light  i.e  $v =c= constant$

For EM waves       $\lambda \times \nu = c =$ constant
Thus waves with highest frequency will have smallest wavelength.