An electron in the c level of a mercury atom
returns to the ground state. which photon
energy could not be emitted by the atom during
this process?
(1) 0.22 ev (3) 4.86 ev
(2) 4.64 ev (4) 5.43 ev

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2   where t1=temperature of cold reservoir ( ° k) = 135            t2=temperature of hot reservoir ( ° k)   = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58%  note: this is the theoretical maximum efficiency of a perfect heat engine.   real-life engines do not achieve this value.