وفّر 50٪ من خلال الاشتراك السنوي في مجرة واحصل على تصفح لا محدود لأفضل محتوى عربي على الإنترنت.
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الرادار، أو الكشف وتحديد المدى بالأمواج الراديوية، هو عبارة عن نظام كشف يعمل اعتماداً على الأمواج الكهرومغناطيسية ذات التردد فوق العالي (UHF) أو الأمواج الميكروية التي تعتبر جزء من الطيف الترددي الراديوي، ويُستخدم لكشف موقع الأشياء أو سرعتها أو كلاهما معاً. يتم توظيف الرادار اليوم في مجال واسع من التطبيقات أهمها التحكم بالحركة الجوية في المطارات، وتوجيه الطائرات والملاحة البحرية والأرصاد الجوية وأنظمة الدفاع الجوي والرصد الفضائي وغيرها.
يعود الفضل في اختراع الرادار إلى مجموعة من العلماء؛ حيث اكتشف الفيزيائي الألماني هاينريش هيرتز أن الأمواج الراديوية تنعكس عن الأجسام الصلبة في عام 1886. وكان المخترع الألماني كريستيان هولسماير أول من استخدم تلك الأمواج لكشف وجود الأشياء المعدنية في عام 1904. ثم في عام 1935 أنتج العالم البريطاني واتسون وات أول نظام رادار عملي.
يتألف نظام الرادار بأبسط أشكاله من مرسل ومستقبل وهوائي؛ ويعتمد على إرسال أمواج كهرومغناطيسية على شكل نبضات قصيرة. وعندما تصطدم تلك النبضات بالأجسام الموجودة في مسارها تنعكس عنها ويعود جزء منها إلى الرادار. يستقبل النظام الأمواج المنعكسة ويجري عليها مجموعة من الحسابات لتحديد موقع الجسم الذي أدى إلى انعكاسها وشعاع السرعة الزاوية لحركته.
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