1. Qhov ntev ntawm lub focal lub lens concave (lub lens sib nrug) 30 cm. Muaj ib yam khoom siab 5 cm nyob rau sab laug ntawm lub lens. Txheeb xyuas qhov nrug ntawm daim duab, qhov loj ntawm daim duab, qhov siab ntawm daim duab thiab cov yam ntxwv ntawm daim duab yog tias yam khoom ntawd nyob deb li 15 cm ntawm lub lens concave.
Kev Sib Tham
Nws yog paub :
Qhov ntev ntawm lub focal (f) = -30 cm
Qhov ntev ntawm lub lens concave yog qhov tsis zoo vim tias qhov chaw ntawm lub lens concave tsis dhau los ntawm lub teeb ci lossis yog virtual.
Qhov siab ntawm yam khoom (h) = 5 cm
Qhov nrug ntawm yam khoom (s) = 15 cm
Nug : Qhov deb ntawm daim duab (s'), qhov loj ntawm daim duab (M), qhov siab ntawm daim duab (h') thiab cov yam ntxwv ntawm daim duab
Jawb :
Duab ntawm kev tsim cov duab ntawm ib yam khoom los ntawm lub lens concave:
Duab nrug (s):
1/s' = 1/f – 1/s = -1/30 – 1/15 = -1/30 – 2/30 = -3/30
s' = -30/3 = -10 cm
Qhov deb ntawm daim duab ntxoov ntxoo tsis zoo txhais tau tias daim duab ntxoov ntxoo yog virtual lossis tsis tau hla los ntawm lub teeb.
Qhov nrug ntawm daim duab ntawm 10 cm me dua qhov nrug ntawm yam khoom ntawm 15 cm.
Kev loj ntawm daim duab (M):
M = -s'/s = -(-10)/15 = 10/15 = 2/3 zaug
Daim duab loj dua txhais tau tias daim duab ncaj los yog tsis tig rov qab.
Qhov loj ntawm daim duab yog 2/3 npaug me dua qhov loj ntawm yam khoom.
Qhov siab ntawm qhov ntxoov ntxoo (h):
M = h'/h
h' = M h = (2/3)5 = 10/3 = 3,3 cm
Qhov siab ntawm tus duab ntxoov ntxoo yog qhov zoo, txhais tau tias tus duab ntxoov ntxoo yog ncaj los yog tsis yog tig rau sab saud.
Daim duab siab 3,3 cm me dua li qhov siab ntawm yam khoom 5 cm.
Cov yam ntxwv ntawm cov duab ntxoov ntxoo
Raws li cov kev xam saum toj no, nws tuaj yeem xaus lus tias cov khoom ntawm daim duab ntawm ib yam khoom tsim los ntawm lub lens concave yog:
- cov duab hluav taws xob lossis lub teeb tsis hla dhau qhov ntxoov ntxoo
- ncaj nraim los yog tsis upside down
- txo qis lossis qhov loj ntawm daim duab me dua li qhov loj ntawm cov khoom
- qhov deb ntawm daim duab me dua qhov deb ntawm cov khoom
2. Ib yam khoom siab 10 cm yog 60 cm nyob rau pem hauv ntej ntawm lub lens concave nrog lub focal ntev ntawm 30 cm. Xam qhov deb ntawm daim duab, qhov loj ntawm daim duab, qhov siab ntawm daim duab thiab cov yam ntxwv ntawm daim duab!
Kev Sib Tham
Nws yog paub :
Qhov ntev ntawm lub focal (f) = -30 cm
Qhov ntev ntawm lub lens concave yog qhov tsis zoo vim tias qhov chaw ntawm lub lens concave tsis dhau los ntawm lub teeb ci lossis yog virtual.
Qhov siab ntawm yam khoom (h) = 10 cm
Qhov nrug ntawm yam khoom (s) = 60 cm
Nug : Qhov deb ntawm daim duab (s'), qhov loj ntawm daim duab (M), qhov siab ntawm daim duab (h') thiab cov yam ntxwv ntawm daim duab
Jawb :
Duab ntawm kev tsim cov duab ntawm ib yam khoom los ntawm lub lens concave:
Duab nrug (s):
1/s' = 1/f – 1/s = -1/30 – 1/60 = -2/60 – 1/60 = -3/60
s' = -60/3 = -20 cm
Qhov deb ntawm daim duab ntxoov ntxoo tsis zoo txhais tau tias daim duab ntxoov ntxoo yog virtual lossis tsis tau hla los ntawm lub teeb.
Qhov nrug ntawm daim duab ntawm 20 cm me dua qhov nrug ntawm yam khoom ntawm 60 cm.
Kev loj ntawm daim duab (M):
M = -s'/s = -(-20)/60 = 20/60 = 1/3 zaug
Daim duab loj dua txhais tau tias daim duab ncaj los yog tsis tig rov qab.
Qhov loj ntawm daim duab yog 1/3 npaug me dua qhov loj ntawm yam khoom.
Qhov siab ntawm qhov ntxoov ntxoo (h):
M = h'/h
h' = M h = (1/3)10 = 10/3 = 3,3 cm
Qhov siab ntawm tus duab ntxoov ntxoo yog qhov zoo, txhais tau tias tus duab ntxoov ntxoo yog ncaj los yog tsis yog tig rau sab saud.
Daim duab siab 3,3 cm me dua li qhov siab ntawm yam khoom 10 cm.
Cov yam ntxwv ntawm cov duab ntxoov ntxoo
Raws li cov kev xam saum toj no, nws tuaj yeem xaus lus tias cov khoom ntawm daim duab ntawm ib yam khoom tsim los ntawm lub lens concave yog:
- cov duab hluav taws xob lossis lub teeb tsis hla dhau qhov ntxoov ntxoo
- ncaj nraim los yog tsis upside down
- txo qis lossis qhov loj ntawm daim duab me dua li qhov loj ntawm cov khoom
- qhov deb ntawm daim duab me dua qhov deb ntawm cov khoom
Teeb meem ntawm lub lens concave
1. Lub lens concave muaj qhov ntev focal ntawm 20 cm thiab ib yam khoom siab 10 cm nyob ntawm qhov deb ntawm 10 cm ntawm pem hauv ntej ntawm lub lens concave. Txheeb xyuas qhov deb ntawm daim duab, qhov loj ntawm daim duab, qhov siab ntawm daim duab thiab cov yam ntxwv ntawm daim duab!
Cov lus teb tseem ceeb:
(a) s' = -20/3 cm
(b) m = 2/3
(c) h' = 20/3 cm
(d) cov yam ntxwv ntawm daim duab: virtual, upright, txo qhov loj me
2. Xam qhov nrug ntawm daim duab, qhov loj ntawm daim duab, qhov siab ntawm daim duab thiab cov yam ntxwv ntawm daim duab ntawm ib yam khoom siab 5 cm thiab 50 cm nyob rau pem hauv ntej ntawm lub lens concave nrog qhov ntev focal ntawm 40 cm!
Cov lus teb tseem ceeb:
(a) s' = -22,2 cm
(b) m = 0,44
(c) siab = 2,2 cm
(d) cov yam ntxwv ntawm daim duab: virtual, upright, txo qhov loj me
