Question 10 What type of spectrum is shown? Explain why we see the bright lines?
Answer 10 Emission Spectrum The bright lines occur when the electrons in an excited gas drop down to their ground state energy level. As they return to the ground state, they emit photons of light at specific wavelengths.
Question 11 One star has a surface temperature of 10,000 K and another has a surface temperature of 40,000 K. How many times more energy is the hotter star emitting?
Answer 11 256 times The 40,000 K star is 4 times as hot as the 10,000 K star. T 4 … 4 4 = 256
Question 12 At what wavelength would a star radiate the greatest amount of energy if it has a surface temperature of 6000 K? Is that within the visible portion of the spectrum?
Answer 12 500 nm Yes, the visible portion of the spectrum is from 400 – 700 nm.
Question 13 Which jump requires the most energy? Which jump would produce a photon with the longest wavelength?
Answer 13 Most Energy -- #3 Longest Wavelength -- #2
Question 14 Identify the spectrum seen from each view point.
Question 15 Which star is brighter, the top or the bottom? How do you know?
Answer 15 The spectral lines on the top spectrum are thinner. Thinner lines mean lower density and brighter. This is because brighter stars tend to be larger (in volume). The larger volume means a lower density (in general).
Question 16 Which star is the coolest? How do you know?
Answer 16 I, the peak wavelength is longer than the other stars. Longer wavelength means less energy means cooler star
Question 17 The top spectrum is at rest. Which spectrum shows a star that is traveling away from us at the fastest rate?
Answer 17 Both spectra show red shift. The bottom one shows more so it is traveling faster.
Question 18 Antares and Betelgeuse are both M class stars. Sirius and Vega are both A class stars. Compare the temperature of these stars to the Sun.
Answer 18 The Sun is a G2 star. The class A stars are hotter than the Sun. The class M stars are cooler than the Sun. O,B,A,F,G,K,M
Question 19 Calculate the Energy and the Frequency of one of the three most intense wavelengths absorbed in this spectrum. (3900 = 390nm)
Answer 19 E = hc/λ and f = v/λ 397.0 nm → 397 x 10 -9 m E = 5.00 E-19 J and f =7.56 E14 Hz 410.0 nm E = 4.85 E-19 J and f = 7.32 E14 Hz 434.0 nm E = 4.58 E-19 J and f = 6.91 E14 Hz