Concept:Light intensity is the amount of light energy received by a surface, and a photometer is the instrument designed to measure it.
Explanation:The question asks for the instrument used in measuring the intensity of light.
Check each option according to what it measures.
Option
A: a thermometer measures temperature, not light.
Option
B: a photometer measures light intensity by detecting electromagnetic radiation, including visible light, ultraviolet light, and gamma rays.
Photometers are widely used in photography, lighting design, and scientific research to determine the brightness of a light source.
Option
C: an anemometer measures wind speed and direction.
Option
D: a hygrometer measures humidity, which is the water vapour content of the air.
Therefore, only the photometer is used for measuring the intensity of light.
Answer:Option
B — photometer.