Why were X-rays named 'X'?

Why were X-rays named 'X'?

• A. Because X is the symbol for the unknown
• B. Because the rays originated from X element
• C. Because the inventor's name started with X
• D. Because they were initially measured with X-ray film

Answer: (A)

X-rays got their name from using X to symbolize an unknown quantity. When Wilhelm Roentgen discovered the rays in 1895, the radiation’s nature was not yet understood, so the unknown was conveniently labeled with the letter X. The term X-ray stuck and became the familiar name, even though we later learned much about their properties. The other ideas don’t fit because there isn’t an X element, Roentgen’s surname doesn’t start with X, and the name wasn’t based on how the rays were measured with film—that usage came later as radiography developed.

X-rays got their name from using X to symbolize an unknown quantity. When Wilhelm Roentgen discovered the rays in 1895, the radiation’s nature was not yet understood, so the unknown was conveniently labeled with the letter X. The term X-ray stuck and became the familiar name, even though we later learned much about their properties.

The other ideas don’t fit because there isn’t an X element, Roentgen’s surname doesn’t start with X, and the name wasn’t based on how the rays were measured with film—that usage came later as radiography developed.