Question

cell phones use what type of electomagnetic wave to operate. a microwaves b radio waves c x rays d uv rays question 20 (2 points) what is the first stage of the life cycle of a star for all stars? a red giant b nebula c protostar d main - sequence

Explanation:

Cell phones use radio waves to communicate. Radio waves are a type of electromagnetic wave that can travel long distances and penetrate obstacles, making them suitable for wireless communication. Microwaves are used in microwave ovens and some wireless communication systems, but not for cell phone operation. X - rays are used in medical imaging and other applications, but they are harmful to living tissue and not used for communication. UV rays are used in some applications such as sterilization and tanning, but they are also harmful to living tissue and not used for communication.

For the second question, the first stage of the life cycle of a star for all stars is a nebula. A nebula is a cloud of gas and dust in space. When a nebula collapses under its own gravity, it forms a protostar. A protostar is a young star that is still gathering mass. As the protostar continues to collapse, it becomes a main - sequence star. A main - sequence star is a star that is in a stable state, fusing hydrogen into helium in its core. When a main - sequence star runs out of hydrogen fuel, it becomes a red giant. A red giant is a large, cool star that is in the late stages of its life cycle.

Answer:

1. B. Radio Waves
2. B. nebula