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How do we catch a cold?

Despite much research, nobody is completely certain why some people catch colds while others do not. Cold research clinics take volunteers in the hope of finding the cause and cure of the common cold but the strange thing is that while some of the volunteers do catch cold, others simply do not become infected. Their natural resistance to the cold …

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How do sunglasses filter ultraviolet rays?

A special clear coating is applied to the lenses, either on the front or back of the lens, or sometimes both sides. It’s a transparent coating and can be applied to any colour of lens including clear. The UV-filtering effect, however, is more complex. UV-filtering lenses are coated with special chemicals that allow light to pass through them, but reflect …

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How do sensor doors work?

Sensor doors use motion sensors or presence sensors. The first are used to activate the door when it detects a moving object, such as a pedestrian or shopping cart. Motion sensors can distinguish between objects moving toward the door or away from it. They use microwave technology, and utilize the Doppler Effect principle. The sensors emit a high frequency microwave …

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How do Satellites Stay Up?

Ten, nine, eight, seven… zero – lift off. These words sound like music to an astronomer’s ears. As the countdown progresses, the rocket’s engines fire and give it the required push to tear through the atmosphere and escape the earth’s gravitation. These rockets take astronauts and artificial or man-made satellites into space. The satellites are used for communication, weather monitoring …

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