Electromagnetic Radiation.

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        I        INTRODUCTION   
Electromagnetic Radiation, waves produced by the oscillation or acceleration of an electric charge. Electromagnetic waves have both electric and magnetic components. Electromagnetic radiation can be arranged in a spectrum that extends from waves of extremely high frequency and short wavelength to extremely low frequency and long wavelength. Visible light is only a small part of the electromagnetic spectrum. In order of decreasing frequency, the electromagnetic spectrum consists of gamma rays, hard and soft X-rays, ultraviolet radiation, visible light, infrared radiation, microwaves, and radio waves.

        II        PROPERTIES  
Electromagnetic waves need no material medium for their transmission. Thus, light and radio waves can travel through interplanetary and interstellar space from the Sun and stars to the Earth. Regardless of their frequency and wavelength, electromagnetic waves travel at the same speed in a vacuum. The value of the metre has been defined so that the speed of light is exactly 299,792.458 km (approximately 186,282 mi) per second in a vacuum. All the components of the electromagnetic spectrum also show the typical properties of wave motion, including diffraction and interference. The wavelengths range from billionths of a centimetre to many kilometres. The wavelength and frequency of electromagnetic waves are important in determining their heating effect, visibility, penetration, and other characteristics.

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        III        THEORY  
The British physicist James Clerk Maxwell laid out the theory of electromagnetism in a series of papers published in the 1860s. He deduced that electromagnetic waves must exist and stated that visible light consisted of such waves.


Physicists had known since the early 19th century that light travels as a transverse wave (a wave in which the vibrations move in a direction perpendicular to the direction of the advancing wave front). They assumed, however, that the wave required some material medium for its transmission, so they thought that there was an extremely diffuse substance, called ether, which was the ...

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The information is laid out clearly and the use of sub-headings is appropriate for this type of writing. In addition technical terms are used adequately and there are no issues with spelling or grammar.

It feels as though some of the paragraphs have been copied and pasted which I strongly discourage against, if you are going to complete this type of essay it must be in your own words. Examiners and teachers are interested in what you have to say and how much you understand. Furthermore there is no conclusion to this piece of writing, which is a mistake. A conclusion is necessary, it helps bring the essay to a close, it summarises your key points and allows you to write personal opinions on the topic you are discussing. Finally the candidate makes several references to experiments and gives quotations. If you are going to do this then it is essential that you provide a full bibliography listing the sources you have used.

The candidate gives a good response and the information provided is scientifically accurate. However their response could be improved by linking together other topics within physics such as polarisation and medical imaging. This shows a wider understanding of physics and is interesting for the reader.