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DOPPLER EFFECT Name __________________________________ Pd _____ Bright-line (emission) spectra are baseline spectra. Dark-line (absorption) spectra indicate Doppler shift. If a star is receding (moving away) from the Earth its wavelengths will be stretched and its spectral lines will be shifted toward the red end of the spectrum. This is called a RED SHIFT. If a star is approaching (moving toward) the Earth its wavelengths will be compressed and its spectral lines will be shifted toward the blue end of the spectrum. This is a called a BLUE SHIFT. To determine velocity (speed & direction) of a star using the Doppler shift we use the following formula: 𝐶 ∆ 𝑉= 𝑏𝑎𝑠𝑒𝑙𝑖𝑛𝑒 V = velocity C = speed of light (186,000 miles/second) = change = wavelength Å = Angstrom (unit for wavelength) PART 1: Star data STAR Antares Procyon Mizar Capella Polaris Arcturus Betelgeuse EMISSION SPECTRA (Å) ABSORPTION SPECTRA (Å) DOPPLER SHIFT DIRECTION OF MOVEMENT VELOCITY (miles per second) 6563 6567 RED AWAY 113.36 4861 4859 BLUE TOWARD 4102 4101 BLUE 4340 4341 5083 5059 6117 6121 6065 6101 WORK STAR Proxima Centauri Sirius Rigel Altair Vega EMISSION SPECTRA (Å) ABSORPTION SPECTRA (Å) 5532 5671 4441 4443 5972 5970 5501 5509 4732 4732 DOPPLER SHIFT DIRECTION OF MOVEMENT VELOCITY (miles per second) WORK PART 2: Star Spectra Use the figure below. Which elements are present in the spectrum of the unknown light source? Compare the light in 2000 and 2015. What is the Doppler shift? What is the direction of movement? What is the velocity? SHOW WORK ABOVE. PART 3: Speed & Direction State the speed and direction of the following stars if their wavelengths are as indicated. Then convert your answers into miles per hour. SHOW WORK BELOW STAR A B C D E 2002 2003 6563 Å 6565 Å 4861 Å 4864 Å 4341 Å 4339 Å 4046 Å 4050 Å 5210 Å 5211 Å DIRECTION SPEED (miles per second) SPEED (miles per hour) PART 4: Speed of Light If a star is moving at 558,000 miles per second, where is its spectral line located now if it was originally at 4861 Å and the object is moving away? SHOW YOUR WORK Explain 2 reasons why questions this is an impossible situation. PART 5: Review Match the definition / description to the words provided. 1. How all the colors in a visible light spectrum differ _______________________________________ 2. What C is the Doppler shift formula represents _______________________________________ 3. What ∆ in the Dopper shift formula resprsents _______________________________________ 4. Type of spectrum which resembles a rainbow _______________________________________ 5. Type of spectrum a neon sign would produce _______________________________________ 6. What a prism does to the light which enters it _______________________________________ 7. Color in the visible light spectrum with the shortest wavelength 8. Unit of wavelength _______________________________________ _______________________________________ 9. Acronym used to remember the order of colors in a spectrum _______________________________________ 10. Name used to describe lines shifting to the blue end _______________________________________ 11. Positive of the bright lines in a spectrum tells you this _______________________________________ 12. As objects move away, the wavelengths get _______________________________________ 13. Redshift tells you an object is moving _______________________________________ 14. What V in the Doppler shift formula represents _______________________________________ 15. If a line shifts from 5004 Å to 5000 Å, the object is moving _______________________________________ ---------------------------------------------------------------------------------------------------------------------------------------------------------------Speed of light Velocity Blue shift Wavelengths Violet Closer Continuous Composition ROY G BIV Angstrom Away Change in wavelength Refracts Longer Emission
