Electromagnetic Radiation vs Electromagnetic Spectrum
Electromagnetic radiation and the electromagnetic spectrum are two widely used concepts in electromagnetic theory. It is vital to have a clear understanding in these phenomena in order to excel in such fields. This article will cover the definitions, similarities and differences of electromagnetic radiation and the electromagnetic spectrum.
Electromagnetic radiation, more commonly known as EM radiation, was first proposed by James Clerk Maxwell. This was later confirmed by Heinrich Hertz who successfully produced the first EM wave. Maxwell derived the waveform for electric and magnetic waves and successfully predicted the speed of these waves. Since this wave velocity is equal to the experimental value of speed of light, Maxwell proposed that light is a form of EM waves. Electromagnetic waves have both an electric field and a magnetic field oscillating perpendicular to each other and perpendicular to the direction of wave propagation. All electromagnetic waves have the same velocity in vacuum. The frequency of the electromagnetic wave decides the energy stored in it. Later it was shown using quantum mechanics that these waves, in fact, are packets of waves. The energy of this packet depends on the frequency of the wave. This opened the field of wave – particle duality of matter. Now it can be seen that electromagnetic radiation can be considered as waves and particles. An object, which is placed in any temperature above the absolute zero, will emit EM waves of every wavelength. The energy, which is the maximum number of photons emitted, depends on the temperature of the body.
Electromagnetic waves are classified into several regions according to their energy. X-rays, ultraviolet, infrared, visible, radio waves are few of them. Everything we see is seen due to the visible region of the electromagnetic spectrum. A spectrum is a plot of intensity versus energy of the electromagnetic rays. The energy can also be represented in wavelength or frequency. A continuous spectrum is a spectrum in which all the wavelengths of the selected region have intensities. The perfect white light is a continuous spectrum over the visible region. It must be noted that, in practice, it is virtually impossible to obtain a perfect continuous spectrum. An absorption spectrum is the spectrum obtained after sending a continuous spectrum through some material. An emission spectrum is the spectrum obtained after the continuous spectrum is removed from the absorption spectrum after the excitation of the electrons. Absorption spectrum and emission spectrum are extremely useful in finding chemical compositions of materials. The absorption or emission spectrum of a substance is unique to the substance.
What is the difference between Electromagnetic Radiation and Electromagnetic Spectrum?
• EM radiation is an effect caused due to interactions between electric and magnetic fields.
• EM spectrum is a quantitative method used to describe the EM radiation.
• EM radiation is a qualitative concept, while EM spectrum is a quantitative measurement.
• The concept of EM radiation alone is useless. EM spectrum has many applications and usages.