How can absorption spectra determine if a star system is a binary pair of stars?

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )

This flow chart shows the amount of energy that is emitted by each type of light. ultraviolet > blue light > yellow light > red light (maximum energy) (minimum energy) in an experiment, shining which type of light on a strip of metal would be least likely to produce the photoelectric effect? ultraviolet light dim blue light bright red light bright yellow light

The chemical formula for emerald is be3al2(sio3)6.an emerald can be decided as