Question 9 A TEM operating at 60 kV has an objective lens po…

Question 9 A TEM operating at 60 kV has an objective lens polepiece with a spherical aberration coefficients of 0.5 mm. (a) Determine the electron wavelength (you can ignore relativistic effects). (2) (b) What is the optimum collection angle and resolution of the microscope in these two polepieces? (ignore chromatic aberration).  (4) (c) If you make the thin lens approximation and assume the objective lens has a focal length of 0.5 mm and is located 0.6 mm after the sample. Make a simple ray diagram sketch showing the object, the lens and the location of the image and diffraction pattern. You diagram should show two rays leaving the object traveling parallel to the optic axis and two rays passing through the center of the lens. (3) (d) What is the magnification of the image in part c). (3)

Question 5:                                                 …

Question 5:                                                                                                                  (4)  Which of the following statements is false about the excitation error, s: a)  It changes the intensity of the g beam leaving the sample b)  It changes the intensity of the g beam associated with a single unit cell c)   It changes when the crystal tilt is changed d)  It changes when the atoms in the unit cell are changed e)  It changes to zero when the exact Bragg condition is satisfied