A single electron has a charge of

Therefore, if we have an excess of

electrons, the total net charge will be the product between the charge of a single electron and the total number of electrons in excess:
The working of a spring is given by:
Entering the unknowns, we have:
If you notice any mistake in my english, please let me know, because i am not native.
Answer:
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).
The fertilized egg or the zygote exists as a single cell until cell division.