In 1886, Heinrich Hertz demonstrated that radio waves that hit objects are reflected, and in 1897, the first accidental radar detection of a ship was performed by Alexander Popov. In 1904, Christian Hulsmeyer made a practical demonstration of intentional detection of metallic objects using a radar.
In 1936, a prototype radar was demonstrated in New York City and detected aircraft from up to 7 miles away. After witnessing the demonstration, the Secretary of War ordered the prototype to be fully developed, and Congress offered $250,000 as funds for its development. The U.S. Army deployed the first fully developed model in 1941 in Hawaii. On Dec. 7, 1941, at 7:02 a.m., the recently installed radar detected aircraft north of its position, and the information was sent to the aircraft warning center. However, the information was misinterpreted as friendly bombers, and 46 minutes later, Pearl Harbor was attacked by Japanese aircraft.Learn More
In large doses, radio waves, also known as radio frequencies, can disrupt biological functions and break down tissue. There is still much debate over whether or not the radio frequencies emitted from mobile communication devices and the systems that support them pose any danger.Full Answer >
Translucent materials allow light to pass through them, but they diffuse the light in a way that make objects on the opposite side appear blurred. Examples of translucent materials are frosted glass, oil paper, some plastics, ice and tissue paper.Full Answer >
Parking sensors use ultrasonic or radio waves that reflect off of objects behind the vehicle to let the driver know how close they are to hitting the object by emitting a beep as a warning. They allow the driver to be more confident while parking and driving in reverse.Full Answer >
The Italian inventor Guglielmo Marconi is credited with inventing the radio in 1895. However, the radio was not just one man’s creation. In 1895, Marconi actually sent out the first telegraphic message. This led to the invention of the radio.Full Answer >