The doppler effect means that all observers of a moving wave source detect the same wave frequency. true or explain

False, it depends on where the source is, and where all observers are located. If some are further than other, then they will feel less of the frequency then those closer, and will not be as affected

hope this helps

No because scientist are still changing there mines today so they are not correct to this day

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.