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Waves & photons

Waves & photons. Waves & photons. What can be measured? λ meters: 0.0 3.0 6.0 9.0

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Waves & photons

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  1. Waves & photons

  2. Waves & photons What can be measured? λ meters: 0.0 3.0 6.0 9.0 Sec: 0.0 0.5 1.0 1.5 wave velocity: c = Δ x/Δ t = 3.0 m/0.5 t = 6.0 m/sec or 9.0 m/1.5 sec =6.0 m/sec Frequency (f = 2 hertz): Complete waves in 1.0 sec: Wavelength (λ= 3.0 m): Linear distance between repetitions: Period (T = 0.5 sec): Time to complete 1.0 wavelength (λ). NOTE: f = 1/T & c = f λ

  3. Waves & photons-Photoelectric effect • Wave particle duality: The wave model explains some properties of light such as diffraction. The particle (photon) model explains other experiments such as the photoelectric effect. One model is used at the exclusion of the other model. • Particle property (energy) is related to the corresponding wave property(frequency): E = hf h = 6.63 X 10-34 j-sec

  4. Waves &photons Problems: c = 3.00 X 108 m/s h = 6.63 X 10-34 j-s 1.0 nm = 1.0 X 10-9 m A microwave oven emits a 2450 Mhz (2450 X 106hz)wave. 1. Calculate the wavelength of this wave. ANS: 0.122 m 2. Calculate the wavelength of this wave in nm. ANS: 1.22 X 108 nm 3. Calculate the energy of one photon. ANS: 1.62 X 10-24 j 4. Calculate the number of photons needed to heat 1pt (454g) of water (c = 4.18 j/g - oC) from 25oC to 100OC. ANS: ΔH = 142,000j (8.79 X 1028 photons)

  5. Waves & photons Problems: c = 3.00 X 108 m/s h = 6.63 X 10-34 j-s 1.0 nm = 1.0 X 10-9 m Police K band radar guns beam a 22.2 ghz microwave (1.0 ghz = 1.0 X109hz )at a car. The reflected wave will have a slightly longer or shorter wavelength (Doppler effect). Or the reflected photon will have less or more energy. The wave and the photon will indicate the automobile's speed. 1. Calculate the wavelength of the beamed wave. ANS: 0.0135m (1.35 X 107 nm) 2. Calculate the energy of the beamed photon. ANS: 1.47 X 10-23j

  6. Waves & photons( Spectra) . c = 3.00 X 108 m/s h = 6.63 X 10-34 j-s 1.0 nm = 1.0 X 10-9 m 1. Calculate the hydrogen green color (λ = 486 nm) light wave frequency. ANS: 6.17 X 1014hz 2. Calculate the energy of each red hydrogen photon. λ = 660 nm ANS: 3.01 X 10-19 j 3. Calculate the photon energy of the shortest wavelength (λ = 490 nm) sodium spectral line. ANS: 4.06 X 10-19 j

  7. Waves &photons c = 3.00 X 108 m/s h = 6.63 X 10-34 j-s 1.0 nm = 1.0 X 10-9 m College of Dupage operates radio station WCDB (90.9 FM = 90.9 X 106 hz) • Calculate the wavelength of the wave in nm. ANS: 3.30 X 109 nm • Calculate the energy of a WCDB photon. ANS: 6.03 X 10-26 j Cobalt-60 is used to treat cancer. Cobalt-60 emits gamma photons at an energy of 1.33 Mev (2.13 X 10-13 j). 3. Calculate the wave frequency. ANS: 3.21 X 1020hz 4. Calculate the wavelength of the wave in nm. ANS: 9.35 X 10-4 nm

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