Kev kho mob ntawm ib lub qhov (slit) - cov teeb meem thiab cov kev daws teeb meem
1. Lub teeb uas muaj qhov ntev ntawm 500 nm hla dhau ib qho qhov uas dav 0.2 hli. Tus qauv diffraction ntawm lub vijtsam deb 60 cm. Txheeb xyuas qhov deb ntawm qhov siab tshaj plaws hauv nruab nrab thiab qhov tsawg kawg nkaus thib ob.
Paub:
λ = 500 nm = 500 x 10 -9 m = 5 x 10 -7 m
d = 0.2 hli = 0.2 x 10 -3 m = 2 x 10 -4 m
l = 60 cm = 0.6 m
n = 2
Xav tau : y?
Tshuaj:
Qhov dav ntawm qhov txiav yog qhov tsawg tshaj plaws piv rau qhov deb ntawm qhov txiav thiab lub vijtsam kom lub kaum sab xis tsawg tshaj plaws (qhov dav ntawm qhov txiav hauv daim duab saum toj no raug nthuav dav). Lub kaum sab xis me heev uas qhov sin θ ≈ tan θ.
sin θ ≈ tan θ = y / l = y / 0.6
Kev sib npaug ntawm d iffraction los ntawm ib qho kev txiav (min ima ):
d sin θ = n λ
(2 x 10 -4 )(y/0,6) = (2)(5 x 10 -7 )
(2 x 10 -4 ) y = (0.6)(10 x 10 -7 )
(2 x 10 -4 ) y = 6 x 10 -7
y = (6 x 10 -7 ) / (2 x 10 -4 )
y = 3 x 10 -3
y = 0.003 m
y = 3 m m
2. Lub teeb monochromatic nrog qhov ntev ntawm 5000 Å (1 Å = 10 −10 m) hla dhau ib qho kev txiav, tsim cov qauv diffraction thawj qhov siab tshaj plaws raws li qhia hauv daim duab. Txheeb xyuas qhov dav ntawm qhov kev txiav.
Paub:
λ = 5000 Å = 5000 x 10 -10 m = 5 x 10 -7 m
sin 30 o = 0,5
n = 1
Xav tau: qhov dav ntawm qhov txiav (d)?
Tshuaj:
d sin θ = n λ
d (0.5) = (1)(5 x 10 -7 )
d = (5 x 10 -7 ) / (0.5)
d = 10 x 10 -7 m
d = 1 x 10 -6 m
d = 1 x 10 -3 hli
d = 0.001 hli
Diffraction yog hais txog qhov xwm txheej uas cov nthwv dej nthuav tawm thaum lawv ntsib ib qho teeb meem lossis hla dhau lub qhov. Thaum lub teeb monochromatic (lub teeb ntawm ib qho wavelength) hla dhau ib qho slit, nws tsis yog tsuas yog mus ncig ua kab ncaj xwb; hloov chaw, nws nthuav tawm thiab tsim ib qho qauv diffraction ntawm lub vijtsam tso tom qab qhov slit.
Rau ib qho kev txiav, qhov tseem ceeb ntawm tus qauv diffraction yog qhov kaj siab tshaj plaws hauv nruab nrab, uas nyob ib sab ntawm ob sab los ntawm cov kab tsaus ntuj thiab ci ntsa iab sib hloov (minima thiab maxima). Nov yog yuav ua li cas nkag siab thiab piav qhia tus qauv diffraction los ntawm ib qho kev txiav:
- Qhov Siab Tshaj Plaws Nruab NrabLub teeb ci ntsa iab nruab nrab yog qhov ci tshaj plaws thiab dav tshaj plaws. Lub zog txo qis thaum ib qho txav deb ntawm qhov siab tshaj plaws hauv nruab nrab.
- MinimaCov kab tsaus ntuj lossis qhov me me tshwm sim ntawm cov ces kaum � xws li: �kev txhaum(�)=�� qhov twg:
- � yog qhov dav ntawm qhov slit.
- � yog qhov wavelength ntawm lub teeb.
- � yog ib qho lej integer, tsis suav tus lej xoom (piv txwv li, ±1, ±2, ±3, …).
- MaximaNruab nrab ntawm cov minima no, muaj cov secondary maxima, tab sis lawv tsis ci npaum li qhov central maximum thiab txo qhov strength ntawm qhov chaw nruab nrab.
- Qhov Dav Dav piv rau Qhov nqaimQhov dav ntawm qhov siab tshaj plaws hauv nruab nrab yog sib piv rau qhov dav ntawm qhov txiav. Qhov ntawd yog, qhov txiav nqaim dua yuav tsim qhov siab tshaj plaws hauv nruab nrab dav dua thiab rov ua dua.
- Ntev dua Wavelength vs. Ntev dua Wavelength Ntev dua Wavelength luv duaCov ces kaum ntawm qhov tsawg kawg nkaus thiab qhov siab tshaj plaws nyob ntawm qhov wavelength. Cov wavelengths ntev dua yuav tsim cov qauv nthuav dav ntau dua piv rau cov wavelengths luv dua.
- Kev sib piv nrog Ob Chav SlitTus qauv diffraction ib qho yog txawv ntawm tus qauv cuam tshuam ob qho, txawm hais tias lawv yog cov xwm txheej cuam tshuam. Yog tias koj muaj ob qho slit, koj yuav pom tus qauv cuam tshuam ntawm ntau qhov ci thiab tsaus ntuj. Txawm li cas los xij, yog tias cov slits dav txaus, txhua qhov slit kuj tseem yuav tsim nws tus qauv diffraction, ua rau muaj qhov "envelope" effect qhov twg qhov hnyav ntawm cov fringes cuam tshuam hloov pauv vim yog ib qho diffraction.
Kev nkag siab txog lej ntawm kev diffraction ib qho siv txoj cai Huygens, uas hais tias txhua qhov chaw ntawm lub nthwv dej tuaj yeem xav txog tias yog qhov chaw ntawm cov nthwv dej kheej kheej thib ob uas nthuav tawm mus rau pem hauv ntej. Los ntawm kev koom ua ke ntawm cov nyhuv ntawm tag nrho cov wavelets no, ib tus tuaj yeem tau txais cov qauv diffraction.
Hauv kev siv ua haujlwm thiab chav kuaj, kev soj ntsuam cov qauv diffraction ib qho tuaj yeem siv los txiav txim siab qhov ntev ntawm lub teeb lossis qhov loj ntawm qhov txiav, muab lwm yam kev ntsuas.
