أكاديميا - كولنز - معاجم الجيب العلمية - الفيزياء - انكليزي - فرنسي - عربي الحرف ١_ r

Academia - Collins - Pocket Scientific Dictionaries - Physics - English - French - Arabic Letter 1_ R


radar
radar m

Radar. A technique that aims to determine the direction and distance of an object by analyzing its reflection of microwaves. Pulses of waves depart in different directions, and the time that elapses before each echo returns is measured. Knowing the speed of radiation allows knowing the distance.

If the body is moving, there is a change in frequency during the reflection, which is called the Doppler effect. This frequency gives the speed of the object, and is a method used by traffic police.


radial circuit
circuit m radial

Radial circuit. Original design of electrical circuits
Household where all power wires radiate from one fuse box to the outlets
And devices. See ring main.


radiation
radiation f

radiation. The transfer of energy by waves or particles. Therefore, any radioactive body loses energy. We have included in this book a description of many types of radiation, and here are two other types:

Heat radiation is the transfer of energy by infrared waves that leave all objects at a rate that depends on temperature. However, black surfaces radiate and absorb these waves better than white surfaces do, unless the temperature is very high.

Cosmic radiation, which consists of very fast particles. The source of this radiation is uncertain, but it may be caused by exploding stars
(Supernovae).
See electromagnetic waves, inverse square, sound, radioactivity, and law.


radio
radio f

Radio. A region of the spectrum of electromagnetic waves - elec tromagnetic waves, whose frequency range ranges between approximately 102 and 107 Hz, and its wavelength range between 10 and 100 meters. “Radio astronomy is very important as it provides us with information about the universe using radio waves that we can Uncover it. However, the most important field in which radio is used is the field of telecommunications. The table below lists the main ranges with approximate data.

the range

LF low frequency
MF medium frequency
HF high frequency
VHF is a very high frequency
UHF ultra high frequency

Wavelength range/meter

103-104
102-103
10 - 102
1 - 10
0.1 - 1

Microwaves are often introduced into the radio region. These waves are also used in telecommunications. Radio communications are carried out with the help of the “ionosphere”, which is part of the upper atmosphere, extending between 40 km and 400 km above the Earth. Many air particles are displaced in the ionosphere mainly by the sun’s ultraviolet rays. Thus, this layer can reflect radio waves.

Homelessness cover
The field closest to the “sky” waves
Ground wave field