We use radar to detect someone far behind or something with signal.

During World War II , the British didn't want the Germans to discover that they were using radar -which was +Technology back then and to complete accurate their night missions.

 

To throw the enemy off the scent, they created the rumor that British pilots were eating copious amounts of carrots which gave them superior vision, thus giving rise to yet another myth - that eating carrots will improve our sight.

 

While the Vitamin A that you can get from carrots is important to the continued healthy functioning of on eyes it doesn't actually improve vision.