# EXSET_4 - Swieter p1 of 5 CHM1040 Question Set#4 QUESTIONS...

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Swieter; p1 of 5 y CHM1040 Question Set #4 QUESTIONS ON THE PROPERTIES OF LIGHT 1. What are the wavelengths, in meters, associated with radiation of the following frequencies? a) 5.09 x 10 14 s -1 b) 8.6 x 10 12 s -1 c) 2.0 x 10 9 s -1 2. What is the frequency and energy (per photon) associated with radiation of each of the following wavelengths? a) 1.8 cm b) 480. Å (1 Å = 1 × 10 -10 m) c) 305 nm 3. What is the frequency and wavelength (in meters) of electromagnetic radiation with the following photon energies? a) 6.95 x 10 -20 J b) 5.96 x 10 -26 J c) 2.00 × 10 -15 J 4. Restate each of the following in the new units indicated and tell in which region of the spectrum it lies: Refer to the attached handout. Example: 5.00 10 15 s -1 to J. First, J is an energy unit and s -1 is a unit of frequency, ν . Therefore, since E = h·v, then, (6.6262 x 10 -34 J·s) × (5.00 x 10 15 s -1 ) = 3.31 x 10 -18 J. a) 150 pm to cm -1 b) 4000 cm -1 to J c) 1.50 x 10 15 s -1 to nm d) 10 cm to J e) 1.0 x 10 -18 J to s -1 f) 1.20 × 10 14 s -1 to cm -1 5. If each atom in one mole of atoms emits a photon of wavelength 650 nm, how much energy is lost? Express the answer in J/mol. As a reference point, burning gaseous CH 4 to form liquid water and gaseous CO 2 produces 890 kJ/mol of heat. 6. Compare the energy of an x-ray photon ( λ = 0.15 nm) with that of a microwave photon ( λ = 1.0 mm). 7. If the human eye receives a 1.59 x 10 -17 J signal from photons whose wavelength is 500 nm, how many photons have hit the eye? 8. Chlorophyll absorbs blue light, λ = 460 nm, and emits red light, λ = 660 nm. Calculate the net energy change in chlorophyll when a single photon of 460 nm is absorbed and one of 660 nm is emitted. 9. The lowest-frequency light that will produce the photoelectric effect on a material is called the threshold frequency . a. If the threshold frequency for Pt is 1.3 x 10 15 s -1 , what is the energy of a quantum of this radiation? b. Will platinum display the photoelectric effect when exposed to ultraviolet light ( λ ~ 100 nm)? Infrared light ( λ ~ 1.00 x 10 -3 cm)?

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Swieter; p2 of 5 y c. What would happen in both cases if the original intensities of the UV and IR light were doubled? d. What would happen if the wavelength of UV light used was decreased.
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EXSET_4 - Swieter p1 of 5 CHM1040 Question Set#4 QUESTIONS...

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