Three students are having a conversation. it goes like this. allison says: "this problem says, can you add a resistor to the circuit so that the current provided to the circuit by the battery increases. how is that possible? for the current to increase, the overall resistance of the circuit has to decrease. doesn't adding a resistor always increase the resistance of the circuit? " nima says: "let's try putting the resistor in series with the other resistors. look, it doesn't matter where we put it, adding it in series always increases the resistance of the circuit, and that decreases the current." natasha says: "that's absolutely right. however, what if we placed the new resistor in parallel with one of the others. look, if we do that, the resistance of that part of the circuit goes down. that has to increase the current from the battery."which of the students are absolutely correct here?

Some material consisting of a collection of microscopic objects is kept at a high temperature. a photon detector capable of detecting photon energies from infrared through ultraviolet observes photons emitted with energies of 0.3 ev, 0.5 ev, 0.8 ev, 2.0ev, 2.5ev, and 2.8ev. these are the only photon energies observed. (a) draw and label a possible energy-level diagram for one of the microscopic objects, which has four bound states. on the diagram, indicate the transitions corresponding to the emitted photons. explain briefly. (b) would a spring–mass model be a good model for these microscopic objects? why or why not? (c) the material is now cooled down to a very low temperature, and the photon detector stops detecting photon emissions. next, a beam of light with a continuous range of energies from infrared through ultraviolet shines on the material, and the photon detector observes the beam of light after it passes through the material. what photon energies in this beam of light are observed to be significantly reduced in intensity (“dark absorption lines”)? explain briefly.