Primer Materials Spring

Transcription

1 Pime Mateials ping

2 Example 8. Calculate the bond stiffness of high puity diamond fom its dielectic constant at low fequencies, ε =5.5. Density of diamond is.55 gm/cm. c 8 m h Js el.6 9 C me kg s F elv mev Nav 6.0 ma.66 7 kg cm 00 mol 5.5 Numbe of atoms pe unit volume Nat.55 gm cm gm Nav mole Nat cm.76 Fo pue electonic polaization 0 Theefoe el Nat mat mat K el Nat K K.5 0 N m if you solved Q than you could figue out that

3 Example 8. Dense fog makes ships invisible to a shot-wave adas (Gz ange cm).. Can you guess why? What conclusion can you daw about the imaginay pat of the dielectic constant of wate at this fequencies?. ome micowave oven woks almost in the same fequency ange (.45 Gz, wavelength of.4 cm). Why?. Can you think of a pactical application of this effect to potect ships? a) wate is stong absobe at this fequencies. Thus the imaginay pat of the dielectic constant is lage. b) home micowave woks at the absoption band of wate to wam the food. c) If you ceate a dense wate spay aound the ship, it will become invisible fo adas.

4 Example 8. The time necessay to bing a small quantity of wate (<50 gm) fom oom tempeatue (5 o C) to a boiling point in a home micowave oven (f=.45 Gz) is pactically independent on the quantity of wate (do not test this at home!!!). The imaginay pat of the dielectic constant of wate at.45 Gz is The time necessay to boil wate is 5 sec. Calculate the stength of the electic field in the oven. What is the eason that such a small electic field can heat so efficiently?

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6 Example 8.4 Mesitylene (,,5-Timethylbenzene, 0.9 g/mol, g/cm, =.4 at 0 C) is used in industy fo a lage vaiety of syntheses. Unfotunately, wate is one of least desiable impuities in it and its content should be thooughly contolled. Until vey ecently, capacitive senso was of one of the most commonly used devices to monito wate content. Please estimate the contibution of wateelated dipoles to the dielectic constant of mesitylene at the wate content of 00 ppm. Dipole moment of wate is.85 D (D=.5-0 C mete)

7 K J KT ; Mesitylene m C p N F m KT p ) ( m dipole N M N A W Mesitylene ) ( 6.75 ) 4.6 ( ) (

8 Example 8.5 dinay glass (sodium glass) has a efactive index of.4. Bohemian glass has a efactive index of.67. Which of these glasses would you like to use as a window glass? Why? Give a numeically motivated answe. ( Conside light passing though a window glass and neglect all inne eflection except fo the fist one) Reflection inceases with inceasing n. Thus to let maximum light in n must be minimized. Tansmission though a thick paallel glass plate is close to be popotional to the squae of the tansmission coefficient at the suface (two eflections oute and inne) n.4 n.67 4n T ( n ) T n T ( n ) T T T.074

9 Example 8.6 UV photolithogaphy uses mios instead of lenses. Why? Calculate the shotest wavelength at which Ag mio can still be used. Use the data fom the lectue notes el.6 9 C c 8 m h Js ev elv s Emeas Emeas.9eV f f z h c.58 7 m f

10 c) Fluoides ae not conductive even if they ae non-stoichiometic. Nonstoichiomety in oxides causes them to be conductive. Theefoe, the efactive index has a lage imaginay pat. o that the Clausius-Mossotti appoach becomes inapplicable. Example 8.7 Density of thin films deposited in vacuum by electon beam evapoation o sputteing is often detemined by compaing thei efactive index with the efactive index of the coesponding bulk mateials.. Why does this method is only applicable fo compaison the films of the same (close) composition?. Deive the fomula elating the densities and the efactive indices.. The method best woks fo fluoides (MgF, CaF ) but it is significantly less accuate fo the case of oxides (i, Ti and Al ). a) the ionic polaizability should be the same. b) Nii ; is density i 0