Move detector around x-ray tube to show that x-rays come out preferentially in the forward direction. Ask for absorbers if you wish. Looking at the close-up photograph at the right above, electrons originate from the electrode at the upper right and strike the anode from its right side, producing x-rays that move preferentially to the right from the cathode.
Note: This demonstration is rather touchy to set up to actually obtain x-rays. It is available largely so that the geometry of such a tube can be seen by the students.