Physics

Electromagnetic Waves and Spectrum

659 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 optics scattering of light and its applications some natural phenomena of light effects of light

In Raman effect, the wavelength of the incident radiation is $5890\overset{o}{A}$. The wavelengths of Stocks and anti-stocks lines are respectively.

  1. $5880\overset{o}{A}$ and $5900\overset{o}{A}$
  2. $5900\overset{o}{A}$ and $5880\overset{o}{A}$
  3. $5900\overset{o}{A}$ and $5910\overset{o}{A}$
  4. $5870\overset{o}{A}$ and $5880\overset{o}{A}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Incident wavelength=$5890 A^{0}$

  • Stocks  lines have wavelength more than the incident radiation
$\lambda _{s}>$ incident wavelength
  • Anti stocks lines have wavelength less than incident radiation
$\lambda _{as}<$ incident wavelength
So the correct option is B

Multiple choice social science universe and space the big bang and the early development of the universe origin of universe evolution of the universe

The wave length of light received from a distant galaxy is 0.5 % greater than that received from an identical source on the earth.the galaxy:

  1. Is stationary relative to the earth.

  2. Is moving towards the earth with velocity of light

  3. Is moving away from the earth with light velocity
  4. Is moving away from the earth with velocity $ 1.5 \times 10^9 m/s $
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The fractional change in wavelength is delta-lambda / lambda = 0.5% = 0.005. For non-relativistic speeds, v/c = delta-lambda / lambda. v = 0.005 * 3 * 10^8 m/s = 1.5 * 10^6 m/s. The option 1.5 * 10^9 m/s is likely a typo for 1.5 * 10^6 m/s.

Multiple choice physics acoustics reverberation applications of reflection of sound multiple reflection of sound and reverberation

RADAR makes the use of.

  1. Infra-red waves of shorter wavelengths

  2. Radio-waves of very short wavelength

  3. Radio-waves of very long wavelength

  4. Ultraviolet waves of longer wavelengths
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

RADAR systems operate by transmitting radio waves of very short wavelengths (microwaves), which reflect off objects to detect their position and speed.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

We consider the radiation emitted by the human body. Which of the following statements is true :

  1. The radiation emitted is in the infrared region

  2. The radiation is emitted only during the day

  3. The radiation is emitted during the summers and absorbed during the winters

  4. The radiation emitted lies in the ultraviolet region and hence is not visible
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Every body at all time, at all temperatures emit radiation (except at T = 0), which fall in the infrared region.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is

  1. Microwaves, Infrared, ultraviolet, gamma rays.

  2. Infrared, Microwaves, ultraviolet, gamma rays.

  3. ultraviolet, gamma rays, Infrared, Microwaves

  4. Microwaves, gamma rays, Infrared, ultraviolet
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The wavelength of the Electromagnetic waves is inversely proportional to the frequency of the wave. The frequency of the gamma rays is highest whereas the ultraviolet, Infrared and microwaves follow in decreasing order.
Therefore, the decreasing order of wavelengths will be opposite to the frequency order. So, the microwaves have the longest wavelength and the gamma rays have the smallest.

Microwave $>$ Infrared $>$ Ultraviolet $>$Gamma ray.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Which of the following rays is emitted  by a human body?

  1. x-rays

  2. visible rays

  3. uvrays

  4. IR rays

  5. none of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

All bodies above absolute zero temperature emit electromagnetic radiation. The wavelength of radiation emitted depends on the temperature of the body. Most of the radiation emitted by the human body is mainly at the wavelength of 12 micron. The wavelength of infrared radiation is between 0.75 to 1000 micron (1 micron = 10-6 metres). Hence , the majority of radiation emitted by human bodies lie in the infrared region.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

M and N are two electromagnetic waves.
The ratio $\dfrac{wavelength of M}{wavelength of N}=10^5$. What could M and N be?

M N
A Microwaves Visible light
B Microwaves $\gamma$-rays
C $\gamma$-rays Microwaves
D Visible light Microwaves


  1. A

  2. B

  3. C

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

The wavelength of microwave is around 5 mm and wavelenght of visible around 500 nm

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Name the radiations of wavelength just longer than $8\times 10^{-7}m$.

  1. infrared

  2. ultrared

  3. infraviolet

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

In the order of increasing wavelength, the waves are Gamma rays ($< 1 nm$), X-rays ($1-10 nm$), infrared rays ($700-{ 10 }^{ 5 }nm$), micro waves (${ 10 }^{ 5 }-{ 10 }^{ 8 }nm$), radio waves (${ >10 }^{ 8 }nm$).
Hence, the radiations of wavelength just longer than ${ 8\times 10 }^{ -7 }m$ is Infrared.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

Fraunhofer spectral lines are called:

  1. Line absorption spectra

  2. Line emission spectra

  3. continuous spectra

  4. Continuous emission spectra
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Fraunhofer spectral lines are also called line absorption spectra. They are a set of spectral lines. The lines were originally observed as dark features (absorption lines) in the optical spectrum of the Sun.