What the frequency of the photon emitted when an electron goes from the 4th energy level (E4 = -0.85eV) to the 3rd energy level (E3 = -1.51eV)
a. 1.59x1014hz
b. 2.05 x1014hz
c. 3.65 x1014hz
d. 5.70 x1014hz

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Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)