Which German scientist discovered the cathode ray?

Which German scientist discovered the cathode ray?

• A. William Crookes
• B. Philipp Lenard
• C. Wilhelm Roentgen
• D. Thomas Edison

Answer: (B)

Cathode rays are streams of electrons produced in a vacuum tube, and understanding their origin and behavior is fundamental to early radiology. The discovery of these rays is credited to William Crookes, a British physicist, who in the 1870s–1880s observed a glow and a beam traveling from the negatively charged electrode to the anode inside a high‑vacuum tube (the Crookes tube). He demonstrated that this beam could move a paddle wheel and cause fluorescence on the tube walls, establishing that a real particle beam was present and that it originated at the cathode. Philipp Lenard, a German physicist, later made pivotal contributions by showing that cathode rays are deflected by electric and magnetic fields and by studying their interactions with metal surfaces. His work helped solidify the particle nature of cathode rays and laid groundwork for later measurements of their properties, but he did not inaugurate the discovery of the rays themselves. Wilhelm Röntgen discovered X-rays, a separate breakthrough relevant to radiology, while Thomas Edison contributed to practical X-ray tube development but did not discover cathode rays. In short, the cathode ray was first observed and described in a way that established the beam’s origin at the cathode by Crookes; Lenard’s work clarified its properties as a charged particle beam, which is why his name often comes up in discussions of cathode-ray research.

Cathode rays are streams of electrons produced in a vacuum tube, and understanding their origin and behavior is fundamental to early radiology. The discovery of these rays is credited to William Crookes, a British physicist, who in the 1870s–1880s observed a glow and a beam traveling from the negatively charged electrode to the anode inside a high‑vacuum tube (the Crookes tube). He demonstrated that this beam could move a paddle wheel and cause fluorescence on the tube walls, establishing that a real particle beam was present and that it originated at the cathode.

Philipp Lenard, a German physicist, later made pivotal contributions by showing that cathode rays are deflected by electric and magnetic fields and by studying their interactions with metal surfaces. His work helped solidify the particle nature of cathode rays and laid groundwork for later measurements of their properties, but he did not inaugurate the discovery of the rays themselves.

Wilhelm Röntgen discovered X-rays, a separate breakthrough relevant to radiology, while Thomas Edison contributed to practical X-ray tube development but did not discover cathode rays.

In short, the cathode ray was first observed and described in a way that established the beam’s origin at the cathode by Crookes; Lenard’s work clarified its properties as a charged particle beam, which is why his name often comes up in discussions of cathode-ray research.