Metal Detector Prank

A metal detector is a device that detects the presence of metal nearby. Metal detectors are useful for finding metal inclusions hidden in objects, or metal objects buried underground. They often consist of a handheld unit with a sensor probe that can sweep the ground or other objects. If the sensor approaches a piece of metal, this is indicated by a changing tone in the earphones, or a moving needle on the indicator. Usually the device gives some indication of distance; the closer the metal, the higher the pitch in the earphone or the higher the needle. Another common type is the stationary "walk through" metal detector (see Security checks below) used at access points in prisons, courthouses, and airports to detect metal weapons hidden in a person's body.
The simplest form of metal detector consists of an oscillator that produces an alternating current that passes through a coil that produces an alternating magnetic field. If a piece of electrically conductive metal is close to the coil, an eddy current will be induced (inductive sensor) in the metal, and this generates its own magnetic field. If another coil is used to measure the magnetic field (acts as a magnetometer), changes in the magnetic field due to metallic objects can be detected.
The first industrial metal detectors were developed in the 1960s and are widely used for mineral searching and other industrial applications. Its uses include detecting landmines, detecting weapons such as knives and firearms (especially in airport security), geophysical searches, archeology and treasure hunting. Metal detectors are also used to detect foreign bodies in food, and in the construction industry to detect steel bars in concrete and pipes and cables buried in walls and floors.
Disclaimer:
This app is a prank app. The metal detector radar in this app is not real, just a kind of simulator.