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 spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

All components of the electromagnetic spectrum in vacuum have the same

  1. energy

  2. velocity

  3. wavelength

  4. frequency
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$Answer:-$ B 

speed of electromagnetic wave in vacuum  is given by:-
c(speed of light)=frequency$\times$ wavelength =$\dfrac{1}{\mu _0 \epsilon _0}$=constant
as we go from gamma rays to radio waves  frequency decreases and wavelength increases thereby maintaining the product constant.

 Energy is given by:- $E=h\nu$ since $\nu$ is different so energy is also different.
Also wavelength and frequency varies.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

In an electromagnetic spectrum, if the rays are placed in increasing order with respect to wavelength (i.e., from lower to higher wavelength); The following order is correct

  1. Radiowaves, microwave, infrared rays

  2. Gamma ray, X-ray, ultraviolet ray

  3. Ultraviolet ray, gamma ray, X-ray

  4. Microwave, infrared rays, radiowaves
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The electromagnetic spectrum in increasing order of wavelength is: Gamma rays, X-rays, Ultraviolet, Visible, Infrared, Microwave, Radio waves.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

PAR range of wavelength is 

  1. $400-700 nm$
  2. $400-800 nm$
  3. $450-950 nm$
  4. $500-600 nm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photosynthetically Active Radiation $(PAR)$ Is the amount of light available for photosynthesis, which is light in the $400$ to $700$ nanometer wavelength range. PAR changes seasonally and varies depending on the latitude and time of day.

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

In electromagnetic spectrum, the frequencies of $\gamma$-rays and ultraviolet rays are denoted by $n _1, n _2$ and $n _3$ respectively then.

  1. $n _1 > n _2 > n _3$
  2. $n _1 < n _2 < n _3$
  3. $n _1 > n _2 < n _3$
  4. $n _1 < n _2 > n _3$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Frequency range of Y rays=${ n } _{ 1 }=>3\times { 10 }^{ 20 }㎐$

Frequency range of ultraviolet rays$={ n } _{ 2 }=7.5\times { 10 }^{ 14 }-3\times { 10 }^{ 17 }㎐$
So frequency of $\gamma$ rays $>$ frequency of ultraviolet rays
${ n } _{ 1 } >{ n } _{ 2 }$

Multiple choice physics spectra the electromagnetic spectrum electromagnetic spectrum electromagnetic waves

The correct sequence of various regions in absorption spectrum is?

  1. Ultraviolet, visible, infra-red, microwave

  2. Microwave, visible, infra-red, X-rays

  3. Infra-red, gamma rays, ultraviolet, microwave

  4. Visible, ultraviolet, microwave, infra-red
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Absorption spectrum is inversly proportional to the wavelength of the wave.

So, the correct sequence will be Ultraviolet, visible, infra-red, microwave as ultraviolet has maximum wavelength and microwave have least wavelength.

Multiple choice chemistry energy : forms and sources renewable and non-renewable resources renewable and non-renewable sources of energy production of electricity from solar energy

In an atomic explosion, a temperature of about 10 million degrees is developed at the moment of explosion. The wavelengths of light corning from the hot region of the atomic explosion lie in the

  1. Ultraviolet region

  2. Visible region

  3. Infrared region

  4. X-ray region
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

lnfrared radiation, often abbreviated as IR, the large band of infrared wavelengths extends from the far-red portion of the visible light spectrum (around 700 - 780 nanometers) to about one millimeter in wavelength. This type of radiation is associated with the thermal region where visible light is not necessarily detectable or even present. As high temperature is developed at the moment of atomic explosion the wavelength of the light coming from that region lie in the infrared region.

Multiple choice

How is an electromagnetic wave disturbed?

  1. when protons bounce off of a medium

  2. when electrically charged particles stop moving

  3. when electrically charged particles vibrate

  4. when neutrons bounce off of a medium
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Electromagnetic waves are generated by the acceleration or vibration of electrically charged particles. This motion creates the oscillating electric and magnetic fields.