Cov nthwv dej sawv ntsug - teeb meem thiab kev daws teeb meem
1. Txoj hlua 3-m raug khi rau ntawm ib kawg thiab lwm qhov kawg txuas nrog lub vibrator. Thaum lub vibrator raug co, txoj hlua tsim ua ib nthwv dej ruaj khov , raws li pom hauv daim duab hauv qab no.
Txheeb xyuas qhov chaw ntawm 5th antinode los ntawm qhov kawg ruaj khov.
Tshuaj:
Qhov nrug ntawm ob lub nodes = 3 meters / 5 = 3/5 meters.
Qhov kev ncua deb ntawm thawj lub node thiab qhov kawg ruaj khov = 3/5 meters
Qhov nrug ntawm qhov thib ob thiab qhov kawg ruaj khov = 2 (3/5 meters) = 6/5 meters
Qhov nrug ntawm qhov thib peb ntawm lub node thiab qhov kawg ruaj khov = 3 (3/5 meters) = 9/5 meters
Qhov nrug ntawm lub node thib plaub thiab qhov kawg ruaj khov = 4 (3/5 meters) = 12/5 meters
Qhov nrug ntawm cov node thiab cov antinode = 1/2 (3/5 meters) = 3/10 meters.
Qhov nrug ntawm qhov antinode thib tsib thiab qhov kawg ruaj khov = qhov nrug ntawm qhov node thib plaub thiab qhov kawg ruaj khov + qhov nrug ntawm qhov node thiab antinode = 12/5 + 3/10 = 24/10 + 3/10 = 27/10 = 2.7 meters.
2. Raws li pom hauv daim duab hauv qab no, ib kawg txuas nrog lub vibrator thiab lwm qhov kawg yog kho. Yog tias txoj hlua ntev yog 1.5 meters, nrhiav qhov deb ntawm qhov thib plaub thiab lub vibrator.
Tshuaj:
Qhov nrug ntawm ob lub nodes = 1.5 meters / 11 = 1.5 / 11 meters.
Qhov deb ntawm thawj lub node thiab vibrator = 1.5 / 11 meters
Qhov deb ntawm lub node thib ob thiab vibrator = 2 (1.5 / 11 meters) = 3/11 meters
Qhov nrug ntawm lub node thib peb thiab vibrator = 3 (1.5 / 11 meters) = 4.5 / 11 meters
Qhov deb ntawm lub node thib plaub thiab vibrator = 4 (1.5 / 11 meters) = 6/11 meters = 0.54 meters
3. Ib txoj hlua muaj ob sab kawg ruaj khov, tsim ib lub suab tseem ceeb nrog zaus ntawm 420 Hz. Txheeb xyuas qhov overtone thib peb.
A. 840 Hz
B. 1260 Hz
C. 1680 Hz
D. 2940 Hz
Paub:
Lub zaus tseem ceeb (f 1 ) = 420 Hz
Ob qho kawg raug khaws cia kom ruaj khov.
Xav tau: lub suab thib peb
Tshuaj:
Thawj lub suab nrov dhau (f 2 ) = 2 f 1 = 2 (420 Hz) = 840 Hz
Lub suab nrov thib ob (f 3 ) = 3 f 1 = 3 (420 Hz) = 1260 Hz
Lub suab nrov thib peb (f 4 ) = 4 f 1 = 4 (420 Hz) = 1680 Hz
Cov lus teb yog C.
4. Lub wavelength ntawm thawj overtone ntawm ib txoj hlua yog 40 cm. Yog tias qhov ceev ntawm lub suab hauv huab cua yog 340 m/s, txiav txim siab qhov overtone thib peb.
A. 850 Hz
B. 1600 Hz
C. 1700 Hz
D. 3200 Hz
Paub:
Qhov ntev ntawm thawj overtone (λ) = 40 cm = 0.4 meters
Qhov ceev ntawm lub suab nthwv dej hauv huab cua (v) = 340 meters/sijhawm
Xav tau: zaus ntawm lub overtone thib peb
Tshuaj:
Hauv qab no yog daim duab ntawm nthwv dej sawv ntsug ntawm ib txoj hlua uas ob sab kawg ruaj khov. Ua ntej, xam qhov ntev ntawm txoj hlua siv qhov ntev ntawm thawj overtone. Tom qab ntawd, ua ntej xam qhov zaus ntawm qhov thib peb overtone, ua ntej, xam qhov ntev ntawm qhov thib peb overtone.
Wavelength ntawm thawj overtone:
Qhov ntev ntawm txoj hlua (L) = 2. ½ λ
Qhov ntev ntawm txoj hlua (L) = λ
Qhov ntev ntawm txoj hlua (L) = 0.4 meters
Wavelength ntawm qhov overtone thib peb:
L = 2 λ
0.4 = 2 λ
λ = 0.4 / 2
λ = 0.2 meters
Zaus ntawm lub suab thib peb:
f = v / λ
f = 340 : 0.2
f = 1700 Hertz
Cov lus teb yog C.
5. Ib lub raj qhib rau ob qho kawg nrog ntev li 40 cm tsim tawm lub suab tseem ceeb nrog zaus ntawm 420 Hz. Txheeb xyuas qhov overtone thib ob.
A. 380 Hz
B. 460 Hz
C. 840 Hz
D. 1260 Hz
Paub:
Qhov ntev ntawm cov yeeb nkab (L) = 40 cm = 0.4 meters
Zaus ntawm lub suab tseem ceeb (f 1 ) = 420 Hertz
Xav Tau: Zaus ntawm lub suab nrov thib ob (f 3 )
Tshuaj:
Yog tias lub suab tseem ceeb (f 1 ) = 420 Hertz ces lub suab thib ob (f 3 ) = 3 f 1 = 3 (420 Hertz) = 1260 Hertz
Cov lus teb yog D.
6. Lub suab nthwv dej ntawm lub raj kaw muaj tus qauv nthwv dej zoo ib yam li ...
A. Kev nthuav dav ntawm nthwv dej ntawm ib txoj hlua
B. Kev nthuav dav ntawm nthwv dej ntawm cov huab cua
C. Nthwv dej sawv ntsug ntawm ib txoj hlua khi rau ib kawg
D. Nthwv dej sawv ntsug ntawm ib txoj hlua khi rau ob qho kawg
Tshuaj:
Ib lub raj kaw yog ib lub raj uas qhib rau ib kawg tab sis kaw rau lwm qhov, raws li pom hauv daim duab saum toj no.
Cov lus teb yog C.
20 cov lus nug thiab lus teb txog cov nthwv dej sawv ntsug:
1. Lo lus nug: Dab tsi yog nthwv dej sawv ntsug?
Lus Teb: Ib nthwv dej sawv ntsug yog ib qho qauv nthwv dej uas zoo li nyob ruaj khov, nrog rau cov nodes thiab cov antinodes, uas yog los ntawm kev cuam tshuam ntawm ob nthwv dej uas mus ncig ua ke.
2. Lo lus nug: Cov nodes thiab cov antinodes sib txawv li cas?
Lus Teb: Cov nodes yog cov ntsiab lus ntawm xoom amplitude, qhov twg nthwv dej tseem nyob twj ywm, thaum cov antinodes yog cov ntsiab lus ntawm qhov siab tshaj plaws amplitude.
3. Lo lus nug: Cov nthwv dej sawv ntsug puas tuaj yeem tsim tau hauv txhua qhov nruab nrab?
Lus Teb: Cov nthwv dej sawv ntsug tuaj yeem tsim tau hauv txhua qhov chaw uas tso cai rau nthwv dej nthuav dav, xws li cov hlua, cov kab cua, thiab dej.
4. Lo lus nug: Lub zaus ntawm nthwv dej sawv ntsug muaj feem cuam tshuam li cas rau nws tus lej harmonic?
Lus Teb: Qhov zaus tseem ceeb (thawj harmonic) yog qhov zaus qis tshaj plaws ntawm nthwv dej sawv ntsug. Cov harmonics siab dua muaj cov zaus uas yog cov lej sib npaug ntawm qhov zaus tseem ceeb.
5. Lo lus nug: Dab tsi txiav txim siab qhov chaw ntawm cov nodes hauv nthwv dej sawv ntsug?
Lus Teb: Cov nodes raug tsim los qhov twg cov nthwv dej mus rau hauv cov kev taw qhia sib txawv cuam tshuam, rhuav tshem ib leeg.
6. Lo lus nug: Cov nthwv dej sawv ntsug tsim tau li cas rau ntawm txoj hlua khi rau ob qho kawg?
Lus Teb: Thaum ib nthwv dej uas mus rau hauv ib txoj hlua cuam tshuam rau ntawm qhov kawg ruaj khov, nws cuam tshuam rau cov nthwv dej uas tuaj txog, tsim ib qho qauv nthwv dej sawv ntsug yog tias cov zaus sib xws nrog qee qhov xwm txheej.
7. Lo lus nug: Kev sib raug zoo ntawm qhov ntev thiab qhov ntev ntawm qhov nruab nrab hauv nthwv dej sawv ntsug yog dab tsi?
Lus Teb: Rau ib txoj hlua khi rau ob qho kawg, qhov ntev ntawm qhov nruab nrab yog tus lej ntau ntawm ib nrab ntawm qhov ntev ntawm nthwv dej sawv ntsug.
8. Lo lus nug: Vim li cas cov nthwv dej sawv tsis hloov pauv lub zog hla qhov nruab nrab?
Lus Teb: Thaum cov khoom me me hauv nruab nrab co, tag nrho cov nthwv dej tseem nyob ruaj khov, yog li tsis muaj kev thauj mus los ntawm lub zog hauv txhua qhov kev taw qhia.
9. Lo lus nug: Koj puas tuaj yeem pom cov nthwv dej sawv ntsug hauv cov raj qhib?
Lus Teb: Yog, cov nthwv dej sawv ntsug tuaj yeem tsim tau hauv cov raj qhib, tab sis cov xwm txheej ciam teb txawv ntawm cov raj kaw, cuam tshuam rau qhov chaw ntawm cov node thiab antinode.
10. Lo lus nug: Yuav ua li cas rau nthwv dej sawv ntsug thaum lub zog ntawm txoj hlua nce ntxiv?
Lus Teb: Qhov ua kom lub zog nruj ntxiv ua rau lub zog nthwv dej ceev zuj zus, uas tuaj yeem hloov qhov zaus thiab tus qauv ntawm nthwv dej sawv ntsug.
11. Lo lus nug: Resonance muaj feem cuam tshuam li cas rau cov nthwv dej sawv ntsug?
Lus Teb: Resonance tshwm sim thaum lub zog sab nraud lossis kev co sib xws nrog lub zog ntuj ntawm lub cev, tsim kom muaj nthwv dej sawv ntsug.
12. Lo lus nug: Lub zaus tseem ceeb yog dab tsi?
Lus Teb: Qhov zaus tseem ceeb, lossis thawj harmonic, yog qhov zaus qis tshaj plaws uas ib lub kaw lus tuaj yeem txhawb nqa nthwv dej sawv ntsug.
13. Lo lus nug: Cov overtones muaj feem cuam tshuam li cas rau harmonics?
Lus Teb: Overtones yog cov zaus saum toj no qhov zaus tseem ceeb. Lub overtone thawj zaug sib raug rau lub harmonic thib ob, lub overtone thib ob rau lub harmonic thib peb, thiab lwm yam.
14. Lo lus nug: Vim li cas ho tsis muaj kev hloov chaw ntawm cov nodes?
Lus Teb: Ntawm cov nodes, ob lub nthwv dej cuam tshuam tsis nyob ntawm theem los ntawm 180 °, ua rau muaj kev cuam tshuam puas tsuaj thiab xoom kev hloov chaw.
15. Lo lus nug: Cov nthwv dej sawv ntsug puas tuaj yeem polarized?
Lus Teb: Cov nthwv dej sawv ntsug ntawm ib txoj hlua yog transverse thiab yog li ntawd muaj kev taw qhia ntawm oscillation (polarization). Txawm li cas los xij, nyob rau hauv ib qho nruab nrab zoo li huab cua, cov nthwv dej sawv ntsug yog longitudinal thiab tsis qhia polarization.
16. Lo lus nug: Vim li cas cov twj paj nruag siv lub hauv paus ntsiab lus ntawm cov nthwv dej sawv ntsug?
Lus Teb: Cov twj paj nruag feem ntau tsim suab los ntawm kev tsim cov nthwv dej sawv ntsug, nrog rau cov harmonics sib txawv tsim cov suab paj nruag sib txawv.
17. Lo lus nug: Qhov ceev ntawm nthwv dej muaj feem cuam tshuam li cas rau qhov zaus thiab qhov ntev ntawm nthwv dej sawv ntsug?
Lus Teb: Qhov ceev ntawm nthwv dej (v) yog qhov sib txawv ntawm zaus (f) thiab nthwv dej (λ): v = fx λ.
18. Lo lus nug: Ob lub zaus sib txawv puas tuaj yeem tsim cov nthwv dej sawv ntsug hauv tib lub nruab nrab?
Lus Teb: Yog, tsuav yog cov zaus sib xws rau cov xwm txheej rau cov nthwv dej sawv ntsug hauv qhov nruab nrab ntawd. Txhua zaus sawv cev rau qhov sib txawv ntawm harmonic.
19. Lo lus nug: Cov nthwv dej sawv ntsug hauv cov raj kaw txawv li cas ntawm cov hauv cov raj qhib?
Lus Teb: Hauv cov raj kaw, ib kawg muaj ib lub node thaum lwm qhov kawg muaj ib lub antinode. Hauv cov raj qhib, ob kawg muaj cov antinodes.
20. Lo lus nug: Puas tuaj yeem tsim cov nthwv dej sawv ntsug nrog txhua zaus hauv ib qho chaw nruab nrab?
Lus Teb: Tsis yog, tsuas yog cov zaus tshwj xeeb uas ua tau raws li cov xwm txheej ciam teb ntawm qhov nruab nrab thiaj li yuav tsim cov nthwv dej sawv ntsug.
Kev nkag siab txog cov nthwv dej sawv ntsug yog qhov tseem ceeb heev rau ntau qhov chaw, txij li suab paj nruag mus rau kev sib txuas lus, vim tias lawv sawv cev rau cov cwj pwm tseem ceeb ntawm cov nthwv dej nyob rau hauv cov xwm txheej tshwj xeeb.
