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 biology asexual reproduction different modes of reproduction sexual and asexual reproduction lifespan, reproduction and variation

Which one of the following wavelengths is more effective for the photo morphogenetic phenomenon?

  1. $730$nm
  2. $680$nm
  3. $660$nm
  4. $560$nm
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photomorphogenesis, particularly the phytochrome-mediated response, is most sensitive to red (660 nm) and far-red (730 nm) light. Far-red light (730 nm) is highly effective at converting Pfr back to Pr, influencing germination and growth.

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 photosystems photosynthesis in plants metabolism, cell respiration, and photosynthesis photosynthesis in higher plants biology

PS I is inactive at

  1. 550 nm

  2. 680 nm

  3. 690 nm

  4. 780 nm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A) PS I can funtion at wavelengths of 700 nm or less. So, it will be active at 550 nm. But its maximum activity is at 700 nm.
B) It will be active at 680 nm.
C) It will be active at 690 nm.

D) PS I cannot function at wavelengths greater than 700 nm.
So the correct answer is '780 nm'.

Multiple choice physics semiconductors band theory of solids, a brief introduction electron energies in solids energy bands

The energy of radiation emitted by $LED$ is :

  1. greater than the band gap of the semiconductor used

  2. always less than the band gap of the semiconductor used.

  3. always equal to the band gap of the semiconductor used.

  4. equal to the or less than the band gap of the semiconductor used
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In an LED, photons are emitted when electrons drop from the conduction band to the valence band. The energy of the emitted photon is approximately equal to or slightly less than the band gap energy.

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 biology protectors of biosphere structure of chloroplast plastids photosynthetic pigments

Photosynthetic Active Radiation (PAR) has the following range of wavelengths

  1. 340-450 nm

  2. 450-950 nm

  3. 500-600 nm

  4. 400-700 nm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Photosynthetic Active Radiation (PAR), designates the special range of solar radiations from 400 to 700 nm that photosynthetic organisms are able to use for the process of photosynthesis.
SO, the correct answer is '400-700 nm'.
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