Chapter 7 - Chapter 7 7.1 Energy and the arrangement of...

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Chapter 7 7.1 Energy and the arrangement of electrons are based on interactions of matter with electromagnetic radiation. One kind of electromagnetic radiation that the eye can see is visible light. Ex: The glow of neon signs in a store window, fireworks on Fourth of July, etc. Atoms gain energy which leads to the electrons becoming excited. This excitement is added energy which after being absorbed by electrons is emitted in the form of electromagnetic radiation. Electromagnetic radiation – consists of oscillating perpendicular electric and magnetic fields that travel through space at the same rate (speed of light = 186,000m/s and 2.998e10 m/s in a vacuum). Frequency and wavelength describe all kinds of electromagnetic radiation. Spectrum – The distribution of intensities of wavelengths or frequencies of electromagnetic radiation emitted or absorbed by an object. Wavelengths in increasing frequency, decreasing wavelength are Radio -> Microwave -> Infrared (10¯³) -> Infrared (10¯ ) -> Visible Light -> Ultraviolet -> X-ray -> Gamma ray In terms of electromagnetic radiation, the intensity depends on the amplitude. So if there is higher amplitude the light is brighter, if there is a smaller amplitude, the light is dim. C= (Wavelength and frequency are inversely related!) λν 7.2 In a toaster wire, the metal atoms gain electric energy and emit radiation in the form of heat. Max Planck came up with a theory to explain why a hot object emits radiation. He said it does so in pockets or packages of energy called quantum. Quantum – A packet of energy
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Quantum Theory – Theory of Max Planck (above.) E=hc/λ (Energy per quantum of radiation increases as wavelength gets shorter.) Photoelectric effect – Certain metals emit electrons when illuminated by light of certain wavelengths. Each atom has a different threshold at which they will emit electrons. Ex: Cs (Cesium) emits electrons at a wavelength of red light but other metals would at yellow light or ultraviolet light. This happens because each wavelength of light has a different amount of energy. (No matter how high the amplitude, if the correct amount of energy is not transmitted, the electron will not be emitted.) Albert Einstein said it was photons and not quantum because photons had both particle- like and wave-like properties. He also said that until the photons had a high enough frequency/low enough wavelengths, the electrons would not be ejected. Photons have a dual nature, which means the photon can behave as a particle and a wave.
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Chapter 7 - Chapter 7 7.1 Energy and the arrangement of...

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