Which of the following is produced by a klystron valve?

The correct answer is Option (1) → Microwaves

Option (1) Microwaves — Correct. Microwaves, with frequencies in the gigahertz range, are produced by special vacuum tubes such as the klystron, the magnetron and the Gunn diode. They are used in radar and in microwave ovens.

Option (2) Light — Incorrect. Electrons in atoms give out visible light when they move from one energy level to a lower energy level.

Option (3) UV rays — Incorrect. Ultraviolet radiation comes from special lamps and very hot bodies such as the sun. It is given out when inner shell electrons in atoms move to a lower level.

Option (4) X-rays — Incorrect. X-rays are produced in X-ray tubes, where high-energy electrons bombard a metal target.

NCERT (2026-27):
Microwaves – “Microwaves (short-wavelength radio waves), with frequencies in the gigahertz (GHz) range, are produced by special vacuum tubes (called klystrons, magnetrons and Gunn diodes).”