-Why can't we be certain that the Andromeda Galaxy existstoday?
-How do sound and light waves differ?
-What is the frequency of a radiowave that has a wavelength of λ = 100 m?
-Which of these is the same for allforms of electromagnetic (EM) radiation in a vacuum (i.e., emptyspace)?
wavelength,frequency, velocity, photon energy
-Which of these is emitted when anelectron falls from a higher to lower orbital?
another electron, a positron, aneutrino, a photon
