1. In about 1675 the Danish astronomer Olaus Roemer found that light from eclips

Question

1. In about 1675 the Danish astronomer Olaus Roemer found that light from eclipses of one of Jupiter's moons took an extra 16.5 min to travel 300,000,000 km across the diameter of the Earth's orbit around the sun. What approximate value for the speed of light did Roemer deduce?
km/s
How much does it differ from our modern value?

2. In one of Michelson's experiments, a beam from a revolving mirror traveled 11 km to a stationary mirror. How long a time interval elapsed before the beam returned to the mirror?
s

3. A certain radar installation used to track airplanes transmits electromagnetic radiation of wavelength 7 cm.

(a) What is the frequency of this radiation, measured in billions of hertz (GHz)?
GHz
(b) What is the time required for a pulse of radar waves to reach an airplane 6 km away and return?
s

Chapter 26 l Previoua Answers In about 167s the Danish astronomer olaus Roemer found that ight tom across the dameter of the Earth's orbit around the edipses of one of Maprter's moons took 303e sun. what approximate value for the speed of ight da Roemer deduce? 10 X km/s an 16s to travel 300.000.00 How much does it differ from our modem vahue? Submit Answer Save Progress 2. O points I Previous Answers Hewitt 1226 E034 In one of Michelson's experiments, a beam from a revolving mirror traveled 11 km to a stationary mirur. How long a time interval elapsed before the beam retuned to the mirror? 3 67E-15 x s Notes Ask 3. 33 I Previous Answers Hewit1226E o35 points The sun is 1.50 x 10 meters from the Earth. How long does it take for the sun's light to reach the Earth?

Explanation / Answer

(1) 16.5 minutes = 990 seconds
3x108/990 = 303,030.3 km/sec (Speed of light that Roemer deduce)
The modern value is 299,792.458 km/sec
Difference from modern value=[(303030.3-299792.458)/299792.458]x100
(3237.842/299,792.458)x100 = .0108x100 = 1.08%

(2)d = 11 km = 11000 m
v (speed of light) = 3 x108 m/s
   v = d / t ==> t = d / v = 11000 / 3 x108= 3.66x10-5 sec.

This is the time for the path in one direction. If you are looking for the time from the revolving mirror to the stationary mirror back to the revolving mirror, then it is twice the above value, which would be 2 x3.66x10-5 sec = 7.33x10-5 sec.

(3) a) the wavelength equation is
speed (of light )= wavelength x frequency
3x108m/s / .07m = f
frequency= 4 285 714 286 hertz
or, 4.285714286 GHz

b) Total distance= 12 km (12000m)
Speed = 3x108 m/s
d=sxt
t= d/s
t= 12000m/3x10^8m/s
t= 0.00004 seconds

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