ज़ेरायोग्राफ़िक (सूखी फ़ोटॉकॉपी) प्रक्रिया का आविष्कार किसके द्वारा किया गया था?

X-rays were discovered by .

Roentgen is related to X-rays in the same way as Becquerel is related to _____?

The first electromagnetic generator, also known as the dynamo, was invented in 1831 by: