Candela was chosen so that the new definition would precisely match the old definition. Although the candela is now defined in terms of the second (an SI base unit) and the watt (a derived SI unit), the candela remains a base unit of the SI system, by definition. If a source emits a known luminous intensity "I" (in candelas) in a well-defined cone, the total luminous flux "Φ" in lumens is given by where "A" is the "radiation angle" of the lamp—the full vertex angle of the emission cone. For example, a lamp that emits 590 cd with a radiation angle
Rosario Candela for him, one of his home and one of his son. Candela began studying cryptography in 1930 after learning about the accomplishments of the Army Signal Corps in WWI. He decrypted messages originally coded in 1898 by Commandant Étienne Bazeries of the French Army. Commandant Bazeries was "one of the most brilliant cryptologists of" his era, and he developed an encryption method considered unbreakable. Candela wrote a book, "The Military Cipher of Commandant Bazeries", in 1938 detailing how he broke Bazeries' code. Starting in 1941, Candela taught a class on cryptography and cryptanalytics at Hunter College in New York. At