The table below shows two types of electromagnetic waves and three random applications of electromagnetic waves.

Type of Wave Application of Waves
Microwaves 1. Show the heat released by astronomical objects
Infrared waves 2. Study stars having high temperature
3. Measure temperature differences in space

Which of these best matches the waves with their applications?

Select one:
a. Microwaves—3 and infrared waves—1
b. Microwaves—1 and infrared waves—3
c. Microwaves—1 and infrared waves—2
d. Microwaves—2 and infrared waves—1

a. Microwaves—3 and infrared waves—1

Explanation:

Microwaves and infrared waves are both part of the electromagnetic spectrum, but they have different frequency and wavelength.

In particular:

- Microwaves are long-wavelength electromagnetic waves, with wavelength between 1 mm and 1 m. Their wavelength is longer than visible light

- Infrared waves are also long-wavelength electromagnetic waves, but their wavelength is shorter than microwaves: between 700 nm and 1 mm. Their wavelength is also longer than visible light.

The two types of waves are also used for different purposes. In particular:

- Infrared waves are emitted by any hot object, and their intensity depends on the temperature of the object. Therefore, they are used in astronomy to show the heat released by astronomical objects (option 1)

- Microwaves are used to study the Cosmic Microwave Background (CMB). This is electromagnetic radiation that permeates the whole universe, and its wavelength depends inversely on the local temperature. Therefore, areas with longer wavelength have lower temperature, and viceversa. Therefore, microwaves are used to measure temperature differences in space (option 3).

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