Operating energy levels in ruby laser are a) energy levels of Al^3+ ions. b) energy levels of O^2- ions. c) energy levels of Cr^3+ r3+ions. Bbibepute ozuH orBer: a. 1) b. 3) c. 2)

The correct answer is:<br /><br />c) energy levels of \(Cr^{3+}\) ions.<br /><br />In a ruby laser, the lasing action occurs due to the transitions between the energy levels of chromium ions (\(Cr^{3+}\)) that are doped into the aluminum oxide crystal.