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CompTIA Security+ 1.2
TechKnowSurge Catalog Interactives What Will the Sensor Read?
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What Will the Sensor Read?

Pallets in the beam, a fan left on, a passing siren. Predict what each sensor reads or each listener hears.

⚑ Complete this interactive to capture a CTF flag worth 5 points.

About this interactive

A microwave or ultrasonic motion sensor sends out waves at one fixed frequency and listens to what bounces back. It never sees the room; it compares the echo with what it sent. Something standing still sends the echo back at the frequency that went out. Something moving toward the sensor meets each wave a little sooner, so the reflected waves bunch up and the echo comes back higher. Something moving away stretches them out, and the echo comes back lower. The faster it moves, the bigger the shift. How far away it is does not shift the frequency at all. The same thing happens when the source itself moves. A siren or a train whistle sounds higher as it comes toward you and lower as it goes away, though its own tone never changes. That is the Doppler effect. Microwaves are electromagnetic waves, and they travel through empty space. Ultrasound is sound, a mechanical wave, pitched above the roughly 20 to 20,000 hertz people can hear, and like all sound it needs air or another medium to travel through. Hearing for the highest pitches fades with age. To predict a reading, ask whether the thing in the beam is moving toward the sensor, away from it, or not at all, and how fast.

What you'll learn

Aligned to

CompTIA Security+
1.2 Summarize fundamental security concepts.

Key terms

Doppler Effect
The observed change in frequency of a wave caused by relative motion between the wave source and the observer, used in radar to detect the speed and direction of moving objects.
Frequency
The number of wave cycles that occur per unit of time, measured in hertz; radar works out an object's speed from how much this number changes in the reflected wave.
Microwave
A range of high-frequency electromagnetic waves used in radar systems to detect and measure the speed of moving objects by analyzing reflected signals.
Ultrasound
Sound waves with frequencies above the human hearing range, typically above 20,000 hertz, used in sensing and imaging applications.
Ultrasonic Sensor
A device that emits ultrasound waves and detects their reflections to measure the distance, motion, or speed of objects.
Motion Detector
A device that senses movement in a defined area and triggers an alert or response, used as a physical security control for deterrence and detection.
Mechanical Wave
A wave that requires a physical medium to travel through, such as sound, as distinguished from electromagnetic waves.
Radar
A detection system that emits microwave signals and analyzes the frequency of reflected waves to determine the speed and direction of moving objects.

Topics

Doppler Effect Microwave Ultrasound Motion Detector Interactive Predict

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