Homework #2 ATOMS AND PHOTONS
Please answer all questions completely. If calculations are required, show enough steps so that I can follow your reasoning.
c = 3 x 108 m/s
h = 6.63 x 10-34 Joule-sec = 4.14 x 10-15
eV-sec
c =λf
E = hf = hc/λ
a. a 1 nm x-rayb. a 3 m radio wave
c. Why is the xray more harmful to humans than the radio wave?
2. Of the three regions of the "optical spectrum" (IR, VISIBLE, UV), which region has the highest energy photons? the lowest energy photons?
3. Glowing hydrogen gas has four visible spectral "lines". These are produced when the electron in the hydrogen atom makes transitions to the energy level labeled E2 in the Figure 1.7 on page 11. The color of light produced is red (the smallest energy jump), blue-green, violet and deep violet. Other lines are also produced by transitions to level E2, but they are not visible.
a. What is the wavelength produced when an atom makes a transition from E3 to E2?d. What is the wavelength produced when an atom makes a transition from E6 to E2?
4. Since the four lines produced by the transitions listed in question 2 are all in the visible region of the spectrum, in what region of the spectrum would the photons produced by the following transitions be found? (Hint: look at the length of the arrows, which is related to the photon energy.)
a. E4 to E1b. E4 to E3
5. What is the difference between an emission spectrum and an absorption spectrum?
6. Why do "glow in the dark" toys continue to glow after the source of energy (light) is removed?
7. All objects not at the absolute zero of temperature radiate blackbody radiation. Since your normal temperature is 98.6oF = 37oC=310 Kelvins (degrees above absolute zero), you radiate electromagnetic energy! Look at Figure 1.9 on page 14 showing the intensity of radiation from three objects at different (and very high) temperature. Explain why some stars appear red and others appear blue.