AST- 105 1st EditionLecture 3Outline of Last LectureI. Astronomy vs. AstrologyII. The Rules of Scientific NotationIII. Light and MatterOutline of Current LectureI. WavesII. SpectraIII. PhotonsCurrent LectureI. Wavesa. The Structure of a Wavei. Crest = high pointii. Trough = low pointiii. Amplitude = heightiv. Wavelength ( “lambda”) = distance between each successive crestv. Frequency (ν “nu”) = number of crests passing at a specific point per timeb. The relation of Wavelength to Frequency i. Speed = wavelength x frequencyii. For electromagnetic radiation, speed = ciii. The relationship between wavelength ( ) and frequency (ν) is an inverse relationship. 1. As ν increases, decreases. 2. As increases, ν decreases.c. There are 2 types of waves:i. Transverse Waves- oscillation is perpendicular to travel direction1. Examples: waves on a string, electromagnetic wavesii. Longitudinal Waves- oscillation is parallel to travel direction1. Examples: sound waves, compression waves on a SlinkyII. Spectraa. Most light contains a range of wavelengthsb. Spectrum- a separation of light into its constituent wavelengths, using a prism or grating.c. Colors of visible light (long to short) are red, orange, yellow, green, blue, indigo, and violet.III. Photonsa. Photon- a packet of energy which acts like a particle. i. All EM radiation is formed of photons, and photons are the smallest unit of all EM radiation. ii. The photons with the most energy are the photons that behave most like a particle.iii. Photon energy: Energy = constant x frequencyb. Properties of Photonsi. The higher the frequency, the higher the energy.ii. The longer the wavelength, the lower the energy. iii. The higher the photon energy, the more particles-like the radiation.1. Radio photons = least energetic2. Gamma-ray photons = most
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