Question

Infrared radiation was discovered in 1800 by
A) William Wollaston
B) William Herschel
C) Wilhelm Roentgen
D) Thomas Young

Answer 1

Hint: Infrared radiation is a part of the electromagnetic spectrum. It was discovered in the 1800 century by using a prism to split infrared radiation from the sunlight and detect the electromagnetic spectrum beyond the visible light.

Complete answer
The discovery of infrared radiation was done by William Herschel who was an astronomer in the early 19th century. William Herschel published his results in 1800. The method he used was through a prism to refract light from the sun and detected the infrared, beyond the red part of the spectrum which is the upper end of the visible spectrum in terms of wavelength. He detected it through an increase in the temperature recorded on a thermometer.
This discovery was possible because of the tendency of infrared radiation to be absorbed by different objects to raise its temperature. This is because infrared radiation has a wavelength corresponding to the energy levels of the intermolecular forces. This means the infrared radiation will be absorbed by the molecules and they will start vibrating more thereby increasing the temperature of the object.
Hence the correct choice is option (B).

Note:
William Herschel called the infrared radiation Calorific Rays and not infrared radiation. The term infrared radiation was used after the 19thcentury. William Wallaston was responsible for the discovery of the chemical elements palladium and rhodium. Wilhelm Roentgen produced and detected electromagnetic radiation in a wavelength range known as X-rays. Thomas Young made a lot of discoveries but he was mainly known for establishing the principle of interference of light.