![]() Wavelengths, frequencies, and energies of light span a wide range the entire range of possible values for light is called the electromagnetic spectrum The full span of the possible wavelengths, frequencies, and energies of light. It is not uncommon to hear light described as photons. What is the frequency of a light wave if its energy is 4.156 × 10 −20 J?īecause a light wave behaves like a little particle of energy, light waves have a particle-type name: the photon The name of a wave of light acting as a particle. This is an extremely small amount of energy-but this is for only one light wave. Seconds are in the numerator and the denominator, so they cancel, leaving us with joules, the unit of energy. Using the formula for the energy of light, we have E = (6.626 × 10 −34 J What is the energy of light if its frequency is 1.55 × 10 10 s −1? The units on Planck’s constant may look unusual, but these units are required so that the algebra works out. s-a very small number that is another fundamental constant of our universe, like the speed of light.Where ν is the frequency of the light, and h is a constant called Planck’s constant The proportionality constant between the frequency and the energy of light. (For most waves, energy is proportional to wave amplitude, or the height of the wave.) The mathematical equation that relates the energy ( E) of light to its frequency is E = h ν It turns out that for light, the energy of the “package” of energy is proportional to its frequency. Light also behaves like a package of energy. What is the wavelength of light if its frequency is 1.55 × 10 10 s −1? A unit in a denominator is indicated by a −1 power-s −1-and read as “per second.” Note how the m units cancel, leaving s in the denominator. We divide both sides of the equation by 5.55 × 10 −7 m and get ν = 5. We use the equation that relates the wavelength and frequency of light with its speed. What is the frequency of light if its wavelength is 5.55 × 10 −7 m? Figure 8.1 "Characteristics of Light Waves" shows how these two characteristics are defined. ![]() Wavelength has units of length (meters, centimeters, etc.), while frequency has units of per second, written as s −1 and sometimes called a hertz (Hz). Wavelength is typically represented by λ, the lowercase Greek letter lambda, while frequency is represented by ν, the lowercase Greek letter nu (although it looks like a Roman “vee,” it is actually the Greek equivalent of the letter “en”). ![]() of light is the number of cycles of light that pass a given point in one second. of light is the distance between corresponding points in two adjacent light cycles, and the frequency The number of cycles of light that pass a given point in one second. The wavelength The distance between corresponding points in two adjacent light cycles. As such, it can be described as having a frequency and a wavelength. We know from experiments that light acts as a wave. What we know as light is more properly called electromagnetic radiation.
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