ความคิดเห็นที่ 20
ความยาวคลื่นยาวทะลุทลวงมากกว่า
เช่นคลื่นน้ำยาว5เมตรเจอไม้5มม.ไม่กั้นคลื่น แต่เจอเรือ50เมตรกั้นได้
ระยะที่คลื่นไปขึ้นกับความยาวคลื่นและขนาดวัตถุที่ขวาง
Longer waves pass around obstacles
A wave on water which is 5 meters long will not be stopped by a 5 mm piece of wood sticking out of the water. If instead the piece of wood were 50 meters big (e.g. a ship), it would be well in the way of the wave. The distance a wave can travel depends on the relationship between the wavelength of the wave and the size of obstacles in its path of propagation.
ความยาวคลื่นยาวทะลุทลวงได้ดีกว่าคลื่นสั้น
It is harder to visualize waves moving through solid objects, but this is the case with electromagnetic waves. Longer wavelength (and therefore lower frequency) waves tend to penetrate objects better than shorter wavelength (and therefore higher frequency) waves. For example, FM radio (88 to 108MHz) can travel through buildings and other obstacles easily, while shorter waves (such as GSM phones operating at 900MHz or 1800MHz) have a harder time penetrating buildings. This effect is partly due to the difference in power levels used for FM radio and GSM, but is also partly due to the shorter wavelength of GSM signals.
http://www.vias.org/wirelessnetw/wndw_04_07_01.html
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เมษ (ชื่อนี้ได้มั้ยฮะ)  
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21 ม.ค. 51 14:50:54
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