# The first model describes light as a continuous wave

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The first model describes light as a continuous wave; the second depicts it as a stream of discreet energy particles. Wavelength is the distance between crests of adjacent waves - Wavelength has a Greek letter symbol, and the unit of nanometers is frequently used to express its value Frequency is the number of waves that pass a given point per second. - Frequency is normally designated by the letter f and is expressed in cycles per second (cps) - The speed of light in a vacuum is a universal constant at 300 million meters per second and is designated by the symbol c. - Frequency = speed of light / wavelength Electromagnetic spectrum is the entire range of radiation energy from the most energetic cosmic rays to the least energetic radio waves - All electromagnetic waves travel at the speed of light (C)and are distinguishable from one another only by their different wavelengths or frequencies. - Similarly, the range of color that make up the visible spectrum can be correlated with frequency. - Lowest frequency of visible light is red; waves with a lower frequency fall into the invisible infrared region - The highest frequency of visible light is violet; waves with a higher frequency extend into the invisible ultraviolet region X ray is a high energy, short wavelength form of electromagnetic radiation Light in any region of the electromagnetic spectrum is a collection of waves possessing a range of wavelengths - Under normal circumstances, this light comprises waves that are all out of step with each other (incoherent light) Laser or coherent light is an acronym for light amplification by stimulated emission of radiation; light that has all its waves pulsating in unison - Light in this form is very intense and can focused on a very small area Photon is a small packet of electromagnetic radiation energy; each photon contains a unit of energy equal to the product of Planck’s constant and the frequency of radiation: E= hf

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- Each photon has a definite amount of energy associated with its behavior. The energy is related to the frequency of light. - E specifies the energy of photon, - F is the frequency of radiation - And h is a universal constant called Planck’s constant. As long as electromagnetic radiation is moving through space, its behavior can be described as that of a continuous wave; however, once radiation is absorbed by a substance, the model of light as a stream of discrete particles must be invoked to best describe its behavior. Th photons of ultraviolet light will be more energetic than the photons of visible or infrared light, and exposure to the more energetic photons of X- rays presents more danger to human health than exposure to the photons of radio waves. Forensic Analyses of Glass Glass that is broken and shattered into fragments and minute particles during the commission of a crime can be used to place a suspect at the crime scene. All of these possibilities required the comparison of glass fragments found on the suspect, whether a person or vehicle, with the shattered glass remaining at the crime scene.
• Fall '19
• Light, Wavelength, refractive index

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