Question 4:                                                 …

Question 4:                                                                              (6) Which of the following statements are true about Howie Whelan equations:     They describe the variation in the intensity of the zero beam for change in the excitation error They describe the variation in the intensity of the diffracted beams with thickness for a particular orientation. They describe the variation in the intensity of the zero beam and diffracted beam for a 2-beam geometry They describe the variation in the intensity of the zero beam and diffracted beam for many beam geometry