5.4 A light source moves in a circular orbit with a speed of 0.5c. What is the displacement, due to the Doppler effect, of the sodium yellow line, as observed at the center of the circle? The line has a wavelength of 589 nm in the laboratory. Ans.: A2 = 91 nm 5.5 The Sun has a radius of 7.0 x 10 m, approximately, and a period of rotation about its axis equal to 24.7 days. What is the Doppler shift of a spectral line with laboratory wavelength 500 nm, in the light emitted (a) from the center of the Sun and (b) from the edges of the Sun's disk at its equator? Ans.: (a) A2 = 1.8 10-8 nm, (b) A 0.00344 nm