Who discovered the cathode ray?

Who discovered the cathode ray?

• A. William Goodspeed
• B. William Crooks
• C. Phillip Lenard
• D. William Conrad Roentgen

Answer: (C)

Cathode rays were first observed in the late 19th century by William Crookes using a partially evacuated glass tube. He noticed a glowing beam that originates at the cathode and travels toward the anode, and showed it could be deflected by electric and magnetic fields and cause fluorescence on a screen. This demonstrated that the beam was a real, charged particle stream, laying the groundwork for later identification of the electron. Phillip Lenard did important work with cathode rays afterward, including electron emission studies, but he did not originate the discovery. Röntgen discovered X-rays, not cathode rays.

Cathode rays were first observed in the late 19th century by William Crookes using a partially evacuated glass tube. He noticed a glowing beam that originates at the cathode and travels toward the anode, and showed it could be deflected by electric and magnetic fields and cause fluorescence on a screen. This demonstrated that the beam was a real, charged particle stream, laying the groundwork for later identification of the electron. Phillip Lenard did important work with cathode rays afterward, including electron emission studies, but he did not originate the discovery. Röntgen discovered X-rays, not cathode rays.