Hope this link might help you.

Does a constantly accelerating charged particle emit EM radiation or not?

This relationship is not an absolute formula.It is just a precise relationship , which has been derieved experimently. Also its not only frequeny (v) mentioned but its ( Vmax) .

This formula only tells you maximum frequency.which you will get corresponding to small energy losses.

In the experiment also when you are applying such a high voltage , and the kinetic energy is very much huge and its take negligible time to cross the tube in (very minimal time).so one can very much safely ignore that.

Hope this link might help you.

Does a constantly accelerating charged particle emit EM radiation or not?

This relationship is not an absolute formula.It is just a precise relationship , which has been derived experimentally. Also it is not only frequency $\nu$ mentioned but its maximal value $\nu_{max}.$

This formula only tells you maximum frequency.which you will get corresponding to small energy losses.

In the experiment also when you are applying such a high voltage , and the kinetic energy is very much huge and its take negligible time to cross the tube in (very minimal time).so one can very much safely ignore that.

Hope that might help you.

Does a constantly accelerating charged particle emit EM radiation or not?

This relationship is not an absolute formula.It is just a precise relationship , which has been derieved experimently. Also its not only frequeny (v) mentioned but its ( Vmax) .

This formula only tells you maximum frequency.which you will get corresponding to small energy losses.

In the experiment also when you are applying such a high voltage , and the kinetic energy is very much huge and its take negligible time to cross the tube in (very minimal time).so one can very much safely ignore that.

Hope this link might help you.

Does a constantly accelerating charged particle emit EM radiation or not?

This relationship is not an absolute formula.It is just a precise relationship , which has been derieved experimently. Also its not only frequeny (v) mentioned but its ( Vmax) .

This formula only tells you maximum frequency.which you will get corresponding to small energy losses.

In the experiment also when you are applying such a high voltage , and the kinetic energy is very much huge and its take negligible time to cross the tube in (very minimal time).so one can very much safely ignore that.