Physics

Electromagnetic Waves and Spectrum

670 Questions

Electromagnetic waves and spectrum questions test a candidate's understanding of radiation frequencies, wavelengths, and the properties of different rays like infrared, ultraviolet, and visible light. Concepts also cover practical applications in astronomy and the fundamental speed of light calculations. This physics topic appears regularly in general science sections of major competitive examinations.

UV rays propertiesElectromagnetic radiation frequencyWavelength identificationSpeed of light calculationsBlack body radiation

Electromagnetic Waves and Spectrum Questions

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

Which one of following have highest frequency?

  1. radio waves.

  2. infrared.

  3. ultraviolet.

  4. gamma rays.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Frequency of Radio waves = $<3\times { 10 }^{ 9 }$Hz

Frequency of infrared waves = $3\times { 10 }^{ 9 }-3\times { 10 }^{ 11 }$Hz
Frequency of ultraviolet waves = $7.5\times { 10 }^{ 14 }-3\times { 10 }^{ 17 }$Hz
Frequency of gamma rays = $>3\times { 10 }^{ 20 }$Hz

So Gamma rays have highest frequency.

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

The wavelength of $X$-rays is in the range

  1. $0.001\mathring { A } $ to $1\mathring { A } $
  2. $0.001 nm$ to $1 nm$
  3. $0.001 \mu m$ to $1 \mu m$
  4. $0.001 cm $ to $1 cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$X$-Rays Wavelength range $=1\times { 10 }^{ -11 }m$ to $3\times { 10 }^{ -8 }m$
So,                          $=0.001 nm$ to $1 nm$

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

Study the frequency of the following electromagnetic radiations and select the correct relationship.
$1$. Infra red
$2$. Microwave
$3$. Ultra violet.

  1. $3 > 2 > 1$
  2. $3 > 1 > 2$
  3. $1 > 2 > 3$
  4. $2 > 3 > 1$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electromagnetic radiation frequency increases in the order: Microwave < Infrared < Ultraviolet. Therefore, Ultraviolet (3) > Infrared (1) > Microwave (2).

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

If a source of power $4$ kW produces $10^{26}$ photons/second, the radiation belongs to a part of the spectrum called:

  1. X-rays

  2. Ultraviolet rays

  3. Microwaves
  4. $\gamma$-rays
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
$4000 \ J$ of energy is produced from $10^{26}$ photons in one second.
Energy of each photon   $E = \dfrac{4000}{10^{26}} = 4\times 10^{-23} \ J$
Frequency of each photon   $\nu = \dfrac{E}{h} = \dfrac{4\times 10^{-23}}{6.63\times 10^{-34}} = 6\times 10^{10} \ Hz$
So the radiation belongs to micro waves.
Correct answer is option C.
Multiple choice

What is the expected sensitivity of LISA?

  1. 10^-23 Hz

  2. 10^-19 Hz

  3. 10^-15 Hz

  4. 10^-11 Hz
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

LISA is expected to have a sensitivity of approximately 10^-19 Hz, allowing it to detect gravitational waves from the early universe.

Multiple choice

What was the sensitivity of the Hubble Space Telescope's instruments?

  1. 10-18 watts per square meter

  2. 10-19 watts per square meter

  3. 10-20 watts per square meter

  4. 10-21 watts per square meter
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Hubble Space Telescope's instruments had a sensitivity of 10-20 watts per square meter, which was much better than any previous space telescope.

Multiple choice

What was the wavelength range of the Hubble Space Telescope's instruments?

  1. 0.1 to 1000 micrometers

  2. 0.1 to 2500 micrometers

  3. 0.1 to 5000 micrometers

  4. 0.1 to 10000 micrometers
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Hubble Space Telescope's instruments had a wavelength range of 0.1 to 1000 micrometers, which covered the ultraviolet, visible, and near-infrared regions of the spectrum.

Multiple choice

What is the wavelength range that ALMA observes?

  1. 1 mm to 10 mm

  2. 100 nm to 1 μm

  3. 10 μm to 100 μm

  4. 100 μm to 1 mm
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ALMA observes millimeter and submillimeter wavelength radiation, which falls between the infrared and microwave regions of the electromagnetic spectrum.

Multiple choice

What is the sensitivity of ALMA?

  1. 100 μJy

  2. 1 mJy

  3. 10 mJy

  4. 100 mJy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ALMA has a sensitivity of 100 μJy, which means it can detect very faint astronomical signals.

Multiple choice

Which region of the electromagnetic spectrum is used to detect the cosmic microwave background radiation, a remnant of the early universe?

  1. Infrared

  2. Ultraviolet

  3. X-ray

  4. Microwave
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The cosmic microwave background radiation is detected in the microwave region of the electromagnetic spectrum, providing valuable insights into the conditions of the early universe.

Multiple choice

What type of electromagnetic wave is emitted by quasars, extremely luminous active galactic nuclei?

  1. Ultraviolet

  2. Infrared

  3. X-ray

  4. Gamma ray
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Quasars emit gamma rays due to the high-energy processes occurring in their central regions, including accretion disks and relativistic jets.

Multiple choice

Which of the following is NOT a type of electromagnetic radiation?

  1. X-rays

  2. Gamma rays

  3. Ultraviolet rays

  4. Sound waves
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sound waves are not a type of electromagnetic radiation. They are mechanical waves that require a medium for propagation.