Scanning Electron Microscopy Coursework Example | Topics and Well Written Essays - 2500 words

Scanning Electron Microscopy - Coursework Example Secondary Electron images (SE) Vs. Backscattered Electron images (BSE)Secondary electron images are formed from the low energy electrons that are formed near the surface of the sample (Johnson). The brightness is affected by the surface topology of the specimen. For backscattered electron images, higher energy electrons formed deeper in the material are used to form the image. The result of these images is less contrast due to surface topology and more contrast due to different chemical composition (Johnson). This explains the 3D nature of the SE image in comparison to the flat BSE image, and the higher contrast of the BSE image in comparison to the SE image.Secondary electrons have lower energy compared to backscattered electrons, and so, they interact with the outer regions of the specimen by inelastic collisions. Therefore, only the surface topology of the specimen is clearly defined. This is the reason why the fibers in the SE looked clumped.The contrast in the BSE image is becau se of the production of backscatter electrons produced due to collisions of high energy electrons of the specimen. Parts of the specimen with higher atomic number cause higher backscatter than the lighter atomic number elements, resulting in a greater contrast, enabling a better study of the chemical composition of the specimen.The greater edge highlight in the SE image is because raised surfaces yield more secondary electrons.... The greater edge highlight in the SE image is because raised surfaces yield more secondary electrons. Images of a tilted TEM grid are provided showing a large difference in depth of field (file names DOF 1, 2, 3). 3 Calculate the depth of field from the images provided. Explain how you arrived at your answer. Compare SEM figures with the depth of field that would be available from an optical microscope for the same magnification. Large depth of field is one of the most important characteristics of SEM. The sharpness of the images recorded at low magnifications depends more on depth of field available than on small beam size (Lyman 1990). We know that depth of field, Where, d = minimum resolution of SEM W = Working distance D = aperture size Accordingly, the depth of field from the given images is computed as follows: Taking the following assumptions, d = minimum resolution of SEM= 3.5 nm = 3.5 ?10-9 m W = Working distance = as given in image in mm ?10-3 m D = aperture size= 200?m = 2 00?10-6 m Depth of field for first image with WD=13.0 mm= 13.0?10-3 m = 0.455?10-6 m = 4.55?10-7 m Depth of field for second image with WD=14.3 mm= 14.3?10-3 m =0.5005?10-6 m = 5?10-7 m Depth of field for second image with WD=44.3 mm= 44.3?10-3 m =1.55?10-6 m Comparison of SEM figures with the depth of field that would be available from an optical microscope for the same magnification The depth of field of SEM can be as great as 300 times that of the optical microscope. At low magnifications, below 300 to 400X, the image formed by the SEM is inferior to that of the optical microscope (Abbaschian et al 2008). At the same magnification, the depth of field that would be

Paranormal Activity 3 Essay Example | Topics and Well Written Essays - 500 words

Paranormal Activity 3 - Essay Example I think that he is not married to Julie because he is two young and he does not belief that marriage itself can reinforce the relationship between the people. He might see proof of that on his work. Toby is the main antagonist of the movie, so to speak. To begin with one should point out that it is a ghost – this is what defines his nature. In addition to that, it manifests itself is a poltergeist which means that it is responsible for creating disturbances in the house of the main characters. Keeping in mind some cruel actions that were done by him, one might conclude that he is also a demon. The reason why it plays trick on people is because it haunts them in order to scare (Montell 140). There is one point when it scratches Randi, a friend of Dennis, and this wound is clearly supernatural as it can not be explained logically. The movie does not say a lot about biological father of the girls; however, I think that he does not call them because his wife and their grandmother killed him. Speaking of the latter, her name is Lois. She wants her daughter Julie to have a son since that is the part of the system of beliefs of the witch coven that she is a part of (Ehrenreich and English 44). At the end of the movie, one might see that Grandma Lois allows Toby to kill her daughter and marry her granddaughter – that is who devoted to the coven she is. Considering the reasons why Toby stalks the babysitter, one might point out that it saw her as an obstacle that could damage its plans, so it was ready to scare her away. The reason why it put on the sheet is largely focused on the fact that prior to that scene, the babysitter put on the sheet too, pretending to be a ghost, so Toby was kind of ironic. There is no particular explanation why it appears to be roughly three feet in height, though Kristi, the only person who