Yuav kom nkag siab txog daim duab ntawm ib yam khoom uas tsim los ntawm daim iav convex , ua tib zoo mloog cov lus nug thiab kev sib tham hauv qab no. Hauv cov lus nug no, nws xav tias yam khoom nyob ntawm qhov deb ntawm daim iav convex, tom qab ntawd piav qhia txog kev tsim cov duab ntawm yam khoom los ntawm daim iav convex , qhov deb ntawm daim duab los ntawm daim iav convex thiab qhov loj ntawm daim duab uas tsim los ntawm daim iav convex.
Xav tias daim iav convex muaj lub vojvoog ntawm qhov nkhaus ntawm 30 cm. Piav qhia txog kev tsim ntawm daim duab, tom qab ntawd txiav txim siab qhov deb ntawm daim duab thiab qhov loj ntawm daim duab yog tias:
a) qhov deb ntawm yam khoom me dua qhov ntev ntawm lub focal (s < f)
b) qhov deb ntawm yam khoom yog tib yam li qhov ntev ntawm lub focal (s = f)
c) qhov deb ntawm yam khoom loj dua qhov ntev ntawm lub lens thiab me dua qhov radius ntawm curvature ntawm daim iav (f < s < r)
d) qhov deb ntawm qhov khoom yog sib npaug rau lub vojvoog ntawm qhov nkhaus ntawm daim iav (s = R)
e) qhov deb ntawm yam khoom loj dua li lub vojvoog ntawm qhov nkhaus ntawm daim iav (s > R)
Kev Sib Tham
Nws yog paub :
Lub vojvoog ntawm qhov nkhaus ntawm daim iav convex (R) = 30 cm
Qhov ntev ntawm daim iav convex (f) = R/2 = 30/2 = -15 cm
Qhov chaw tseem ceeb ntawm daim iav convex yog tom qab daim iav convex qhov twg lub teeb tsis hla dhau qhov chaw tseem ceeb ntawm daim iav convex, yog li ntawd qhov chaw tseem ceeb ntawm daim iav convex tau muab lub cim tsis zoo.
Jawb :
Qhov nrug ntawm yam khoom me dua qhov ntev ntawm lub iav convex (s < f)
Xav tias qhov deb ntawm cov khoom ntawm daim iav yog 5 cm thiab 10 cm.
1) Qhov nrug ntawm lub teeb (f) = -15 cm thiab yog tias qhov nrug ntawm lub teeb (s) = 5 cm
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/5 = -1/15 – 3/15 = -4/20
s' = -20/4 = -5 cm
Lub cim tsis zoo rau qhov nrug ntawm daim duab (s') txhais tau hais tias daim duab yog virtual lossis daim duab nyob tom qab daim iav convex qhov twg lub teeb tsis dhau los ntawm daim duab.
Qhov nrug ntawm tus duab ntxoov ntxoo (s') 5 cm yog tib yam li qhov nrug ntawm tus khoom (s) 5 cm
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-5)/5 = 5/5 = 1 zaug
Kev nthuav dav kab ntawm daim duab (M) 1 txhais tau tias qhov loj ntawm daim duab zoo ib yam li qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
2) Qhov nrug ntawm lub teeb (f) = -15 cm thiab yog tias qhov nrug ntawm lub teeb (s) = 10 cm
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/10 = -2/30 – 3/30 = -5/30
s' = -30/5 = -6 cm
Lub cim tsis zoo rau qhov nrug ntawm daim duab (s') txhais tau hais tias daim duab yog virtual lossis daim duab nyob tom qab daim iav convex qhov twg lub teeb tsis dhau los ntawm daim duab.
Qhov nrug ntawm daim duab (s') 6 cm me dua qhov nrug ntawm yam khoom (s) 10 cm.
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-6)/10 = 6/10 = 0,6 zaug
Qhov linear magnification ntawm daim duab (M) yog me dua 1, txhais tau tias qhov loj ntawm daim duab yog me dua qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
Qhov nrug ntawm cov khoom yog tib yam li qhov ntev ntawm lub iav convex (s = f)
Qhov ntev ntawm lub zeem muag (f) = qhov nrug ntawm yam khoom (s) = 15 cm.
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/15 = -2/15
s' = -15/2 = -7,5 cm
Lub cim tsis zoo rau qhov nrug ntawm daim duab (s') txhais tau hais tias daim duab yog virtual lossis daim duab nyob tom qab daim iav convex qhov twg lub teeb tsis dhau los ntawm daim duab.
Qhov nrug ntawm daim duab (s') 7,5 cm me dua qhov nrug ntawm yam khoom (s) 15 cm.
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-7,5)/15 = 7,5/15 = 0,5 zaug
Qhov linear magnification ntawm daim duab (M) yog me dua 1, txhais tau tias qhov loj ntawm daim duab yog me dua qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
Qhov nrug ntawm yam khoom loj dua qhov ntev ntawm lub lens thiab me dua qhov radius ntawm curvature ntawm daim iav convex (f < s < R)
Xav tias qhov deb ntawm cov khoom ntawm daim iav yog 20 cm thiab 25 cm.
1) Qhov nrug ntawm lub teeb (f) = -15 cm thiab yog tias qhov nrug ntawm lub teeb (s) = 20 cm
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/20 = -4/60 – 3/60 = -7/60
s' = -60/7 = -8,6 cm
Lub cim tsis zoo rau qhov nrug ntawm daim duab (s') txhais tau hais tias daim duab yog virtual lossis daim duab nyob tom qab daim iav convex qhov twg lub teeb tsis dhau los ntawm daim duab.
Qhov nrug ntawm daim duab (s') 8,6 cm me dua qhov nrug ntawm yam khoom (s) 20 cm.
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-8,6)/20 = 8,6/20 = 0,4 zaug
Qhov linear magnification ntawm daim duab (M) yog me dua 1, txhais tau tias qhov loj ntawm daim duab yog me dua qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
2) Qhov nrug ntawm lub teeb (f) = -15 cm thiab yog tias qhov nrug ntawm lub teeb (s) = 25 cm
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/25 = -25/375 – 15/375 = -35/375
s' = -375/35 = -10,7 cm
Qhov nrug ntawm daim duab (s') yog qhov tsis zoo, txhais tau tias daim duab yog virtual lossis daim duab nyob tom qab daim iav concave qhov twg lub teeb tsis hla dhau daim duab.
Qhov nrug ntawm daim duab (s') 10,7 cm me dua qhov nrug ntawm yam khoom (s) 25 cm.
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-10,7)/25 = 10,7/25 = 0,4 zaug
Qhov linear magnification ntawm daim duab (M) yog me dua 1, txhais tau tias qhov loj ntawm daim duab yog me dua qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
Qhov nrug ntawm cov khoom yog sib npaug rau lub vojvoog ntawm qhov nkhaus ntawm daim iav convex (s = R)
Lub vojvoog ntawm qhov nkhaus ntawm daim iav (R) = qhov deb ntawm qhov khoom (s) = 30 cm.
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/30 = -2/30 – 1/30 = -3/30
s' = -30/3 = -10 cm
Lub cim tsis zoo rau qhov nrug ntawm daim duab (s') txhais tau hais tias daim duab yog virtual lossis daim duab nyob tom qab daim iav convex qhov twg lub teeb tsis dhau los ntawm daim duab.
Qhov nrug ntawm daim duab (s') 10 cm me dua qhov nrug ntawm yam khoom (s) 30 cm.
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-10)/30 = 1/3 zaug
Qhov linear magnification ntawm daim duab (M) yog me dua 1, txhais tau tias qhov loj ntawm daim duab yog me dua qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
Qhov nrug ntawm yam khoom loj dua li lub vojvoog ntawm qhov nkhaus ntawm daim iav convex (s > R)
Xav tias qhov deb ntawm cov khoom ntawm daim iav yog 40 cm thiab 50 cm.
1) Qhov nrug ntawm lub teeb (f) = -15 cm thiab yog tias qhov nrug ntawm lub teeb (s) = 40 cm
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/40 = -8/120 – 3/120 = -11/120
s' = -120/11 = -10,9 cm
Lub cim tsis zoo rau qhov nrug ntawm daim duab (s') txhais tau hais tias daim duab yog virtual lossis daim duab nyob tom qab daim iav convex qhov twg lub teeb tsis dhau los ntawm daim duab.
Qhov nrug ntawm daim duab (s') 10,9 cm me dua qhov nrug ntawm yam khoom (s) 40 cm.
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-10,9)/40 = 10,9/40 = 0,3 zaug
Qhov linear magnification ntawm daim duab (M) yog me dua 1, txhais tau tias qhov loj ntawm daim duab yog me dua qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
2) Qhov nrug ntawm lub teeb (f) = -15 cm thiab yog tias qhov nrug ntawm lub teeb (s) = 50 cm
Duab nrug (s') :
1/s' = 1/f – 1/s = -1/15 – 1/50 = -10/150 – 3/150 = -13/150
s' = -150/13 = -11,5 cm
Lub cim tsis zoo rau qhov nrug ntawm daim duab (s') txhais tau hais tias daim duab yog virtual lossis daim duab nyob tom qab daim iav convex qhov twg lub teeb tsis dhau los ntawm daim duab.
Qhov nrug ntawm daim duab (s') 11,5 cm me dua qhov nrug ntawm yam khoom (s) 50 cm.
Kev nthuav dav ntawm daim duab (M) :
M = -s'/s = -(-11,5)/50 = 11,5/50 = 0,2 zaug
Qhov linear magnification ntawm daim duab (M) yog me dua 1, txhais tau tias qhov loj ntawm daim duab yog me dua qhov loj ntawm cov khoom.
Qhov linear magnification ntawm daim duab (M) yog positive, txhais tau tias daim duab yog upright.
