'(<a href="http://www.j-archive.com/media/2005-03-23_J_17.jpg" target="_blank">Sarah of the Clue Crew reports from a metal detector at JFK Airport in New York.</a>)  A metal detector creates this type of field--if a sort of echo of the field comes back, metal must be present'
a magnetic field
HOMELAND SECURITY: A metal detector creates this type of field--if a sort of echo of the field comes back, metal must be present
A metal detector creates this type of field--if a sort of echo of the field comes back, metal must be present
A metal detector creates this type of field--if a sort of echo of the field comes back, metal must be present
HOMELAND SECURITY
a magnetic field
HOMELAND SECURITY