The Empire State Building has several FM antennas on top, added in part to
increase its overall height. These antennas aren't very tall. Why do short
antennas, located high in the air, do such a good job of transmitting FM
radio? - ANS ✓FM radio transmission involves high-frequency, short-wavelength
radio waves and since a good antenna is one-quarter wavelength long, FM radio
transmission requires relatively short antennas.
(High-frequency radio waves travel in straight lines between antennas
which therefore results in a limit of approximately 100 km (60 mi) on FM
radio transmissions, even if the antennas are on top of a very tall building.)
Why are most microwave TV dinners packaged in plastic rather than
aluminium trays? - ANS ✓Aluminium trays would reflect the microwaves which
would result in improperly cooked food.
(The plastic trays allow microwaves to pass through which allows the
food's water, sugars, and fats to absorb the microwaves.)
PHY 102
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PHY
Compare how a potato cooks in a microwave oven with how it cooks in an
ordinary oven. - ANS ✓In a microwave oven, the potato's water absorbs
microwaves and that microwave energy becomes thermal energy and the
potato's temperature rises uniformly. In an ordinary oven, heat flows gradually
into the potato through its surface and its temperature rises nonuniformly with
the middle of the potato last to become cooked.
When you're listening to FM radio near buildings, reflections of the radio
wave can make the reception particularly bad in certain locations. Compare
this effect to the problem of uneven cooking in a microwave oven. - ANS
✓Both involve destructive interference in electromagnetic waves.
(Destructive interference in electromagnetic waves results in poor
receptions and uneven cooking.)
Radio waves travel through empty space - ANS ✓at the speed of visible light.
Imagine being an observer watching a light wave travel by you, much like
you would watch a car travel by you on the highway. If you could detect the
electric field at your location, you would observe - ANS ✓the electric field
undulating up and down as the wave travels to the right or left.
The speed of light is about - ANS ✓299 million meters per second.
PHY 102
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