1-4 The standard of leng Ith The first international standard of length was a bar of a platinum-iridium alloy called the standard meter In 1960. the 1 1 th cgpm defined the meter as the length of 1, 650, 763. 73 wave length of a special radiation of Kr86 In 1983. the 17th CGPM redefined the meter as the length of the path traveled by light in vacuum during a time interval 1/299.792 458 of a second1-4 The standard of length • The first international standard of length was a bar of a platinum-iridium alloy called the standard meter. • In 1983, the 17th CGPM redefined the meter as the length of the path traveled by light in vacuum during a time interval 1/299,792,458 of a second. • In 1960, the 11th CGPM defined the meter as the length of 1,650,763.73 wave length of a special radiation of Kr86