What type of energy is stored in the earths crust and produces earthquakes

Two friends at different locations want to communicate with each other by sending low energy signals. which of the following methods can they use to communicate? a) produce x-rays using colliding electrons and send them to radios, which capture sound b) send messages using infrared radiation, which travel in the form of waves c) send radio waves through intervening media like radio and television d) produce sound waves using microwaves from heated objects

What is the maximum number of electrons that an atomic orbital can contain?

Apiece of metal with a length of 1.42 cm was measured using four different instruments. which of the following measurements is the most accurate?