QUIZ 1 - AY4 - W04 . . . . . . . . . . . . . . YOUR NAME: Mike Possibly useful formulae: λmax (cm) = 0.29 T(K) ; λ × f = c (wavelength x frequency = speed) Speed of light = c = 300,000 km/sec 1. How long does it take light to travel from the Moon to the Earth, a distance of 384,000 km? By the way, did you remember to write your name on the quiz? Time=Distance/Speed=3.84x10 5 km 3x10 5 km sec 3.84 = seconds 3 2. The reason we experience different seasons is: a) The Earth’s orbit around the Sun is an ellipse so sometimes we are closer to the Sun (summer), sometimes we are further from the Sun (winter). b) The Earth spins on its axis. c) The spin axis of the Earth around its center is tilted with respect to the orbital axis of the Earth around the Sun. c) None of these answers is correct. 3. The speed of light is c = 186, 000 miles/second. Calculate the speed of light in units of miles/minute. 186,000 miles second x 60 seconds = 186,000 x 60 miles/minute minute 4. Rank the following in order of increasing frequency (1 - highest; 5 - lowest): 1 X-rays 4 FM radio (800 MegaHertz) 2 Blue light 5 AM radio (800 kiloHertz) 3 Infrared 5. A source emits infrared radiation at a wavelength of 1060×10−9 m. What is the frequency of this radiation? f=c/ wavelength = 3x10 5 km/sec 1km −9 m x 1060 x 10 1000m = 3 1060 17 x 10 1/sec 6. Suppose you have a hot (i.e. collisionally excited) gas of hydrogen and a hot gas of helium, each at the same temperature. Label the following statements True (T) or False (F). f The two gases would have identical spectra f Both gases would show identical emission-line spectra t The two gases would show different emission-line spectra f Both would show continuous spectra, with the helium-gas spectrum peaking at a shorter wavelength