1. Week 8 LO5 Vikrom Sethinamvong
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Learning Objectives
The Doppler Effect
How do Radar Towers to locate aircrafts?
When two objects move towards each other, the received frequency is higher, and if they are
moving apart, the received frequency is lower.
- Radar towers emit pulses that are reflected
back by objects.
- The radar tower sends off pulses in all
directions around it with equal frequency,
because the wave fronts are all equally
spaced and all travel at the same speed.
As an aircraft moves further from the
the radar tower, the pulse sent out by
the tower is reflected back by the
aircraft with a lower frequency.
Stationary objects reflects back the pulse with the same frequency that approaches it, thus the
air navigators can tell the difference between objects that are stationary and moving.
As the aircraft returns towards the radar
tower the pulse reflected of it has a higher
frequency than the one originally sent out by
the radar tower.
- long and short frequencies are used to
differentiate between the directions at which
objects are moving. The frequencies are all
filtered once picked by the radar tower
making it applicable for reading on a radar
map.
In this case the source of the pulses remains stationary
because it does not move. The only thing that moves, is the
receiver which are the aircrafts that fly by.
Eqaul frequencies of pulses are sent out by the radar tower in
all directions, and the frequency delivered by the source and
received by the receiver can be connected by this relationship:
, where r is receiver and s is source.
