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The EM Spectrum

When most people think of the word “light” they are probably talking about visible light, but the electromagnetic spectrum is much bigger and more diverse than that. Visible light is actually a very small part of the electromagnetic spectrum. Lets break down the spectrum in terms of wavelength. Visible light has a wavelength of 390 to 700 nanometers. X-rays and gamma rays, on the other hand, have wavelengths from 1 nm to 1 pm (1×10^-12). AM radio waves have a wavelength of 200-600 meters. In other words the wavelength of AM radio waves is about 1 trillion times as long as the wavelength of visible light. Light waves can have very different wavelength, so they can also have very different energy. Waves with shorter wavelength have higher energy. This is why some light is so dangerous and some is not. Gamma rays and even x-rays can be lethal, while radio waves and visible light are around us all the time.


Photo source: Wikipedia

Feb 27 Solar Eclipse

On February 27, 2017 there will be an annular solar eclipse visible in parts of the South America and Southern Africa. A solar eclipse happens when the moon gets between the earth and the sun. An annular solar eclipse is like a total solar eclipse but instead of blocking all the visible light from the Sun it blocks all of the light except a ring around the outside. But what causes a solar eclipse to be annular? The moon’s orbit is elliptical, so it is sometimes closer to the Earth and sometimes further. When the moon is at or near apogee (the point in its orbit that takes it farthest from Earth) it appears smaller to an observer on Earth. Therefore when the moon eclipses the sun at apogee it does not appear to cover the entire sun. Instead it only covers part. When it lines up correctly, the relatively distant and apparently smaller moon creates an annular eclipse on the sun. solar-eclipse-annular

Photo cred: timeanddate.com