the mean of 16 terms was found to be 30 it was found that two terms were wrongly taken ad 22 and 18 as 32 and 28 respectively . Find the correct mean

Figure shows a simple cathode-ray tube. a beam of particles, emitted by the cathode, strikes the centre of the screen.a. why the cathode must be heated? b. what is the principal energy change that occurs when the beam strikes the screen? c describe and explain what you would expect if the two deflecting plates g and h were connected to an alternating voltage supply