ws2f09key - CH301 Fall 2009 Worksheet 2 Answer Key A Lovely...

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CH301 Fall 2009 Worksheet 2 Answer Key: A Lovely Worksheet on the First 2/3rds of Chapter 1. Great for Quiz 1. 1. Calculate wavelength from the following frequencies. a) 625 kHz λ = c/ν λ = (3.00 E8 m/s)/(625 E3 Hz) = 480. m b) 734 MHz λ = (3.00 E8 m/s)/(734 E6 Hz) = .409 m c) 8.4 E14 Hz λ = (3.00 E8 m/s)/(8.4 E14 Hz) = 3.6 E-7 m d) 92 GHz λ = (3.00 E8 m/s)/(92 E9 Hz) = 3.3 E-3 2. Given the following energies, calculate the frequencies of the photons. a) 17 kJ ν = E/h ν = 17000 J/6.63 E-34 J·s = 2.6 E37 s -1 b) 564 E-25 J ν = 564 E-25 J/6.63 E-34 J·s = 8.51 E10 Hz c) 98 pJ ν = 98 E-12 J/6.63 E-34 J·s = 1.5 E23 Hz d) 230 J ν = 230 J/6.63 E-34 J·s = 3.5 E35 s -1 3. Rank the wavelengths of the photons in question 2 from longest to shortest. Use A, B, C, or D to identify the photon. (Hint: No calculations necessary.) B C D A Remember that wavelength and energy are inversely related (E = h·c/λ) – the higher the energy, the shorter the wavelength. 4. The double slit experiment is a famous demonstration of the wave nature of light: when light of a single frequency is passed through two parallel sits in a barrier, it produces an interference pattern on a surface placed on the other side. Draw an example of an interference pattern (as amplitude of light received vs. position). Compare the frequency and phase of the light waves coming from the two slits at the dark spots and at the light spots on the interference pattern. An interference pattern looks something like this: At the dark spots, the two waves still have the same frequency as the original light source, but have opposite phase causing them to cancel (destructive interference). At the light spots, the frequency is also the same but the phase is identical, causing constructive interference. 5. When passed passed through very fine gratings (or even regular crystals), electrons and neutrons form a distinctive pattern of ridges and troughs because of their wave nature. What is this effect called? The scattering of waves by lattices (the fancy name for a grating) is called diffraction. Fun fact: X-rays were first identified as light waves in the 19th century by the fact that they were diffracted by crystals. Knowing what we do now about the wave nature of matter,
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would we necessarily draw the same conclusion from that evidence? 6. The description of light as a collection of particles goes back to long before quantum
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ws2f09key - CH301 Fall 2009 Worksheet 2 Answer Key A Lovely...

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