The electromagnetic (EM) spectrum is the range of all types of Electromagnetic radiation. Radiation is energy that travels and spreads out as it goes – the visible light that comes from a lamp in your house and the radio waves that come from a radio station are two types of electromagnetic radiation.
Electromagnetic waves are transverse waves which results from oscillating electric and magnetic fields at right angles to each other.
Electromagnetic spectra are arranged in order of their wavelength or frequency. This arrangement forms what is known as the electromagnetic spectrum.
A complete spectrum is shown below:
The figure below shows electromagnetic waves arranged in order of decreasing wavelengths
Properties of Electromagnetic waves
The Electromagnetic waves have the following common properties.
- They travel through vacuum(space) with a speed of 3.0 x 108ms-1 . This speed is usually referred to as the speed of light in vacuum and is usually denoted by c.
- Do not require material medium for transmission
- They are transverse in nature
- Electromagnetic waves undergoes interference, reflection,refraction and polarisation effect
- Posses energy in different amounts according to the relation E=hf where h is the Plank’s constant given as 6.63 x 10-34 Js and f is the frequency
- They carry no charge
- They are not affected by electric or magnetic fields
Example: calculating energy of a wave
A certain electromagnetic radiation was found to be having a wavelength of 6.5 x 10-8 m. Calculate the energy it emits.
solution
To calculate the energy of a wave, you need to know its frequency. Then multiply the frequency by Planck’s constant.
Here we have only the wavelength, but we can get the frequency from the relation: v = fλ.
since it is an electromagnetic wave, it’s speed is 3.0 x 10-8 ms-1. and hence f=v/λ. that is:
=4.6154 x 1015 HZ
The energy of a wave was defined as E = hf where h (plank’s constant)= 6.63×10−34 Js
hence E = 6.63 x 10-34 Js x 4.6154 x 1015 HZ≈ 3.06 x 10-20J.
Related Topics
- Angular velocity
- Waves
- Calculating speed of a wave
- Types of waves
- Characteristics of a wave motion
- Trigonometric ratios
- Equation of a circle
References
- Secondary Physics Student’s Book Four. 3rd ed., Kenya Literature Bureau, 2012. pp.
- Abbot A. F. (1980), Ordinary Level Physics, 3rd Edition, Heinemann Books International,
London. - Nelkon M. and Parker P., (1987), Advanced Level Physics, Heinemann Educational Publishers, London.
- Tom D., and Heather K. Cambridge IGCSE Physics. 3rd ed., Hodder Education, 2018, https://doi.org/978 1 4441 76421.