Introductory Physics Volume Two
Introductory Physics Volume Two
Introductory Physics Volume Two
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148 Wave Optics 7.6<br />
• The minimum power occurs when the phase difference is an odd<br />
multiple of π. The waves as said to be directly out-of-phase.<br />
• When the phase difference is an odd multiple of π/2, the power is<br />
equal to the sum of the powers of the individual signals.<br />
⊲ Problem 7.8<br />
Suppose that you are at home talking on your wireless phone, and you<br />
walk near your refrigerator. Since the refrigerator is made of metal<br />
it acts as a reflector for the microwave signal going to and from your<br />
phone. Because of this there are two paths between your phone and<br />
the transceiver (the base that phone sits in) that it is communicating<br />
with.<br />
x<br />
Phone<br />
Refrigerator<br />
Transceiver<br />
When you are a distance x from the refrigerator the signal that reflects<br />
from the refrigerator must travel a distance 2x further. Assuming that<br />
the reflected amplitude is one half of the direct amplitude, graph the<br />
power of the signal as a function of your distance from the refrigerator.<br />
Assume that the wavelength of the signal is 10cm. Are there places<br />
that it would be better to avoid?<br />
§ 7.6 Interferometer<br />
It is possible to build a device that measures very small motions<br />
by using interference.<br />
The device represented in the diagram below is called an interferometer.
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