A photon was absorbed by a hydrogen atom in its ground state, and the electron was promoted to the forth orbit. When the excited atom returned to its ground state, visible light
was emitted. In this process, radiation of what wavelength must. have been emitted (R=
1.097 x10' m )? Explain.

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

How much energy moves onto the next level, in an energy pyramid

Which sentence about particles in matter is true? a. atoms are present in solids and liquids but not in gases. b. the particles of matter are in constant motion. c. the same kinds of atoms are found in different elements. d. when a solid changes to a liquid, the sizes of the particles change.