Astronomy 102 Problem Set #1

due February 3, 2000, 5:00 pm, Olin Science 174

Problem #1: The Cassini spacecraft is currently on its way to Saturn and will arrive in 2004. Right now (January 23, 2000) it is 1.5 million km from the asteroid Masurski, and 380 million km from Earth. How long do radio signals from this spacecraft take to reach controllers here on Earth?

Problem #2: a) How many green photons (wavelength = 500 nm) does it take to equal the energy of one gamma ray photon (wavelength = 10^-2 nm)?
b) How many of these gamma ray photons would it take to equal the the energy required to light a 100-watt light bulb for one second (100 J)?

Problem #3: a)The public radio station in Lewisburg broadcasts at a frequency of 100.1 MHz ("mega-hertz"). What is the wavelength of these radio waves?
b)I'm driving in my car at 55 mph (24.6 m/s) directly toward the radio station's broadcast tower. What is the frequency shift (due to the Doppler Effect) in the signal my car radio receives? Is the received frequency higher or lower than the broadcast frequency?