Electromagnetic spectrum visible part

Different types of electromagnetic radiation make up the electromagnetic spectrum. Visible light - the radiation that our eyes can detect - makes up only a small part of the electromagnetic spectrum. 

Nonetheless, our primary interest lies in the 0.4 to 0.7 micron range, which we call the visible part of the electromagnetic spectrum. Note that even bodies at liquid-eiir temperatures emit photons between 10 and 100 microns in wavelength, i.e.- 100,000 and 10 A in wavelength. The earth itself at a temperature of 300 °K. has an emission between about 20,000 and 300,000 A... 

Near-infrared Spectroscopy. Near-infrared spectroscopy (NIRS) uses that part of the electromagnetic spectrum between the visible and the infrared. This region has the advantage that the instrumentation is nearest to visible instrumentation. Signals in the near-infrared come not from the fundamental vibrations of molecules but from overtones. As... 

So, the [Fe(H20)6]2+ ion will absorb radiation with a wavelength of 780 nm, which is red light in the visible part of the electromagnetic spectrum. 

The reference beam. This is the other light path. It s not visible light but another part of the electromagnetic spectrum. Just remember that the reference beam is the one farthest away from you. 

Figure 12.3 Regions of the electromagnetic spectrum in terms of both frequency (hertz) and wavelength (m). The visible region is a very narrow band between 400 and 700 nm. The lower labels show which part of the atom the various radiations correspond to, i.e., X-rays result from reorganization of the inner shell electrons, UV from the valence electrons, etc. From PSSC PHYSICS, second edition, copyright 1965 by D. C. Heath and Company. Used by permission of Houghton Mifflin Company.

You probably recall that visible light is part of a broader continuum of energy called the electromagnetic spectrum. Figure 3.6 reviews the key properties of the electromagnetic spectrum of energy. 

There are definite distinct lines in the atomic emission spectrum of hydrogen. These lines are seen in the visible part of the spectrum and there is also a series of lines in the infrared and another series in the ultraviolet part of the electromagnetic spectrum. So, although hydrogen is the simplest element with only one electron per atom, its atomic emission spectrum is fairly complicated. 

Think back to the split d orbitals. Electrons in the lower energy d orbitals can absorb energy and move to the higher energy d orbitals. If the energy absorbed in these so-called d-d transitions is in the visible part of the electromagnetic spectrum, the colour of the transition metal compound will be the complementary colour of the absorbed colour. So the colour we see will be white light minus the colour absorbed. 

The effects of d-d transitions can be studied using spectroscopy. If the absorbed energy is in the visible part of the electromagnetic spectrum, giving a coloured compound, visible spectroscopy is used. If the absorbed energy is in the ultraviolet part of the electromagnetic spectrum, the compound will be colourless and ultraviolet spectroscopy is used. 

Infrared radiation comprises that part of the electromagnetic spectrum that lies between microwaves and visible light (see p. 6). When it is absorbed by organic compounds, the energy is sufficient to cause the bonds within the molecules to vibrate, but not enough to break the bonds. 

The trapped electron provides a classic example of an electron in a box . A series of energy levels are available for the electron, and the energy required to transfer from one level to another falls in the visible part of the electromagnetic spectrum, hence the colour of the F-centre. There is an interesting natural example of this phenomenon The mineral... 

Infrared (IR) radiation refers broadly to that part of the electromagnetic spectrum between the visible and microwave regions. Of greatest practical use to the organic chemist is the limited portion between 4000 and 400 cm-1. There has been some interest in the near-IR (14,290-4000 cm-1) and the far-IR regions, 700-200 cm-1. 

Figure 23-1 A part of the electromagnetic spectrum. The letters Vy By G, Y, O, R over the visible part of the spectrum refer to the colors of the light. The position marked "Ka line of Cu" is the wavelength of X-rays and most widely employed in X-ray diffraction studies of proteins and other organic materials.

Infrared (IR) radiation refers broadly to that part of the electromagnetic spectrum between visible and microwave regions. IR spectroscopy is one of the most powerful... 

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