Light and the Electromagnetic Spectrum


Energy native the Sun

Nearly every (99.97%) the the energy we have actually on Earth comes from the sun. This amounts to an median of 340 joules/second because that every square meter of the Earth"s surface.Solar power is nuclear energy. It originates from the fusion reactions that occur in the sun. In a combination reaction, two tiny nuclei merge to type the cell nucleus of a larger atom. Part mass is convert to power in the process. Below is a typical combination reaction. An isotope of hydrogen, deuterium or 2H, combine with one more isotope the hydrogen, tritium or 3H, to form helium and also a neutron.

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The deuterium nucleus is composed of 1 proton and also 1 neutron v an atom mass of specifically 2.0. Tritium has actually 1 proton and also 2 neutrons (3.0 amu). The helium nucleus has actually a fixed of 3.98 amu and the free neutron is 1.0 amu. In this reaction some mass, 0.02 amu, is converted right into energy.E = mc2 where c, speed of irradiate = 2.998 x 108 m/secRemember that the joule (J) is the typical unit of energy. We deserve to convert any kind of other unit of energy into joules or kilojoules (kJ). Over there are plenty of online conversions programs to aid with the calculations. For instance 1 joule is equal to 1 (kilogram)(meter)2/(seconds)2.In the last lecture you saw that sun, like any type of other warm object, release its energy in discrete "rays" that have actually some nature of particles and also some nature of waves. We call it electromagnetic radiation.
There is a circulation of energies the the radiation the looks similar to circulation of kinetic energies the atoms and also molecules in ~ a substance. Many graphs of power distributions have actually a comparable shape.Notice the radiation in the visible light range is close come the average energy for the solar spectrum however there is quite a bit of radiation an ext and less energetic than this.You radiate energy, too. The radiation native a human body of around 310 K is in the infrared range.

Electromagnetic radiation

Electromagnetic radiation is the type of power that includes light, heat, and x-rays. It have the right to be defined using a sinusoidal tide model, wherein the nature of the radiation rely on the wavelength, frequency, and other parameters the the wave. For part purposes, it makes an ext sense to define the power as a stream of light particles called photons, whereby the power of the photons is proportional come the frequency of the radiation. Wave nature of electromagnetic radiation:Amplitude (A): The elevation of the waveWavelength (λ): The distance in between two crests the the waveCrest and also trough: The highest and lowest points, respectively, of a wave Speed of irradiate ( c ): The velocity the radiation as it travels v a vacuum. This quantity is the very same for all develops of electromagnetic radiation, indigenous x-rays to light to radio waves, and also is continuous within a particular transportation medium.The rate of light in vacuum is 2.99792 x 108 m/s. The speed of irradiate in wait is only 0.03% slower, and also c in either medium is usually just rounded turn off to 3.00 x 108 m/s.

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Frequency (ν): The variety of waves the pass a fixed allude per secondPeriod (T): The variety of seconds the takes for a tide to happen a solved point
ν = 1/T - The frequency that the tide is the mutual of the period.λ ν = c (or ν = c/λ) - the product of frequency and wavelength is the speed of light. Alternatively, the frequency the a wave is inversely proportional come the velocity.E = hν = hc/λ , where h is the Planck constant, 6.626 x 10-34 - The power of the radiation is same to the Plank consistent multiplied by the frequency that the radiation.

The Electromagnetic Spectrum

Although all waves the electromagnetic radiation take trip at the rate of light, different varieties of waves have actually vastly different wavelengths, frequencies, and energies. The shorter the wavelength that the radiation, the higher the frequency and also the bigger the energy. The electromagnetic spectrum varieties from gamma (γ) radiation, which has actually the shortest wavelength, highest possible frequency, and also greatest energy, to radio waves, which has actually the longest wavelength and lowest frequency and also energy.
Ultraviolet irradiate (UV) is divided into 3 regions:UV A, wavelength = 400 - 320 nmUV B, wavelength = 320 - 280 nmUV C, wavelength = Visible light is between 750 nm (red) and 400 nm (violet). Mental Roy G. Biv?BackCompassTablesIndexIntroductionNextProfessor Patricia Shapley, college of Illinois, 2012