Electron Microscope & Onion Peel Cells (PDF)

shor,rrn in Figure 5, an electron microscope is a verv large instrument that uses electromagnets for magnification and electrons for illumination. This remarkable instrument was developed bv Knoll and Ruska of Germany h 1932 and it v"as put to use in 1940. lt uses very high voltage As k electricity....

shor,rrn in Figure 5, an electron microscope is a verv large instrument that uses electromagnets for magnification and electrons for illumination. This remarkable instrument was developed bv Knoll and Ruska of Germany h 1932 and it v"as put to use in 1940. lt uses very high voltage As k electricity. Electron microscope helps ir !n** electron gun specimen position binocular viewer control panei obserwing subcellular structures.uvhich cannot be seen through a compound microscope An internal vacuum is essential for its u,orking. The object must be ultra thin and dry. It is impregnated with some metal to enhance contrast. The image of the object is obtained on a photographic film or scruen' Magnification is 100,000 to 500,000. Electron microscoPe. Figure 5. An electron microscoPe. of forceps, we can peel off the skin Let us take an ir-u-rer fleshY leaf of onion bulb. with the help of a set of the onion' This layer can (called the epidermis; it is one cell thick) from the concave side (inner layer) water' This will avoid the peel be put immediately in a petridish ( a glass dish) or watch-glass containing getting folded and getting drv a1so. What do we do with this onion Peel? piece of peel from the petridish Let us take a glass slide, put a drop of clean water on it ancl transfer a You may need a thin camel or ivatch-g1ass to the slide. Make sure that peel is perfectly flat on the slide. iodine solution on the piece of hair paint brush to help you to transfer the peel. At this stage put a drop of mount of onion peel' You onion peel followed by a cover slip. In this way you have PrePared a temporary comPound rnicroscope (Figure 4)' can observe this slide under the low and high porver of a light that you are able What do vou observe as You look through the lens? Can you draw the structures look like the Figure 68' to see through the microscope in t'our obserrration sheet? Does it ffi\R \ if f I t3t'4 a 1 a= celis in the snion peel AB iinirrrr A---. ,:: *:,--.=:.*::of ,,,-,'. ,. onionpeel onamicroscopicslide; B-Thecellsoftheonionpeel' onion peels with different sizes, you will observe that they all and together they form a big have similar sma-, :::r::.--r-: - :-.e s. srruclures look similar to each other see in an onion peel are structure such as a:- -- -- - - :- : -. -:- - : e:- sn-ra1l microscopic structures that you. : I r^.:se structures are called cells. Not only onion but all organisms tltebssicbuilding uni;:.. rr --^.. -.,:--_- thatyouseearoundsr€ 12 -:::- rl--; rr- -- - ---j ,-.f l= -: :' '='-s The Fundomentol Unit of Life: Cell