Ngaphambi kokuthola ifomula yesibuko esigobile, qala ngokuqonda imithetho eminingana yezimpawu zesibuko esigobile.
Imithetho Yesibonakaliso Sesibuko Esigobile
- Ibanga lezinto (ama)
Uma into iphambi kobuso besibuko obubonisa ukukhanya khona-ke ibanga lento (s) kuyinto enhle.
- Ibanga lesithombe (s')
Uma isithunzi siphambi kobuso besibuko obubonisa ukukhanya, lapho ukukhanya kudlula khona esithunzini, khona-ke ibanga lesithunzi (s') kuyinto enhle (isithombe sangempela). Uma isithombe singemuva kobuso besibuko obubonisa ukukhanya, lapho ukukhanya kungadluli khona esithombeni, khona-ke ibanga lesithunzi kuyinto engemihle (isithombe esibonakalayo).
- Irediyasi yokugoba (R)
Isikhungo sokugoba kwesibuko esigobile siphambi kobuso obubonisayo besibuko, ngakho-ke irediyasi yokugoba yesibuko esigobile inhle. Uma irediyasi yokugoba inhle, ubude obuqondile (f) nabo bunhle.
- Ukuphakama kwento (h)
Uma into ingaphezu kwe-axis eyinhloko yesibuko esigobile khona-ke ukuphakama kwento (h) kuyinto enhle (into eqondile). Ngokuphambene nalokho, uma into ingaphansi kwe-axis eyinhloko yesibuko esigobile khona-ke ukuphakama kwento kuyinto engemihle (into ephendukezelwe).
- Ukuphakama kwesithunzi (h')
Uma isithombe singaphezu kwe-axis eyinhloko yesibuko esigobile khona-ke ukuphakama kwesithombe (h') kuhle (isithombe siqondile). Uma isithombe singaphansi kwe-axis eyinhloko yesibuko esigobile, ukuphakama kwesithombe kubi (isithombe siguquliwe).
- Ukukhulisa isithombe (m)
Uma ukukhulisa isithombe > 1 khona-ke usayizi wesithombe mkhulu kunosayizi wento. Uma ukukhulisa isithombe = 1 khona-ke usayizi wesithombe ufana nosayizi wento. Uma ukukhulisa isithombe < 1 khona-ke usayizi wesithombe mncane kunosayizi wento.
Ifomula Yesibuko Esigobile
Bheka isithombe esingezansi. Kunemisebe emibili yokukhanya eboniswa esibukweni esigobile, bese imisebe yokukhanya iboniswa yisibuko esigobile. 
Isihlokwana:
s = ibanga lento, s' = ibanga lesithombe, h = P P' = ukuphakama kwento, h' = Q Q' = ukuphakama kwesithombe, F = indawo egxile esibukweni esigobile.
Isithombe esingenhla sibonisa imisebe yokukhanya emibili, okungukuthi i-P'BFQ' kanye ne-P'AQ'. Imisebe yokukhanya i-P'AQ' ithobela umthetho wokukhanya, ngakho-ke unxantathu i-P'AP ufana ne-Q'AQ. Ngakho-ke:
![]()
Ku-light beam P'BFQ', unxantathu i-BFA ufana ne-QFQ' lapho ibanga u-AB = ukuphakama kwento (h) kanye nebanga u-FA = ubude obuqondile (f) besibuko esigoqekile. Ngakho-ke:

Izinhlangothi zesobunxele nesokudla zezibalo 1 no-2 ziyalingana, ngakho-ke izinhlangothi zesokudla ziyalingana:

Phindaphinda izinhlangothi zombili zesibalo ngo-s' :

Incazelo yefomula:
s = ibanga lento (into enhle uma into iphambi kobuso besibuko esigobile esibonakalisa ukukhanya)
s' = ibanga lesithombe (elihle uma isithombe sento siphambi kobuso besibuko esigobile esibonakalisa ukukhanya noma isithombe singokoqobo)
f = ubude obuqondile (obuhle uma indawo eqondile yesibuko esigobile itholakala phambi kobuso besibuko esigobile esibonisa ukukhanya)
Khumbula njalo umthetho wesibuko esigobile lapho usebenzisa le fomula ukuxazulula izinkinga zesibuko esigobile.
Ukukhuliswa Kwesithombe (m)
Bheka isithombe sokwakheka kwesithunzi sento ngenhla. Onxantathu i-PAP' kanye ne-QAQ' bayafana, ngakho-ke singathola ubudlelwano phakathi kwebanga lento kanye nebanga lesithunzi nokuphakama kwento kanye nokuphakama kwesithunzi:
![]()
Imininingwane:
h = ukuphakama kwento (okuqondile uma into ingaphezu kwe-axis eyinhloko yesibuko esigobile noma into eqondile. Okungalungile uma into ibheke phansi)
h' = ukuphakama kwesithombe (okuqondile uma isithombe singaphezu kwe-axis eyinhloko yesibuko esigobile noma isithombe esiqondile. Okungalungile uma isithombe siphendukezelwe)
s = ibanga lento (elihle uma into idluliswa umsebe wokukhanya wesigameko)
s' = ibanga lesithombe (elihle uma isithombe sidlula ngomsebe wokukhanya noma isithombe sangempela. Elibi uma isithombe singadlulanga ngomsebe wokukhanya noma isithombe esibonakalayo)
Ifomula engenhla ingabhalwa kabusha njengoba ingezansi ngokungeza uphawu m:
![]()
Imininingwane:
m = ukukhuliswa kwesithombe
Imibuzo Yesibonelo Yesibuko Esigoqekile
I-Pelajari isibonelo sesibuko esigobile ukuze uqonde kangcono indlela yokusebenzisa ifomula yesibuko esigobile.
1. Ingane ima phambi kwesibuko esigobile ukuze isithombe esakhiwe siqonde futhi sibe sikhulu kabili kunengane. Uma ukugoba kwesibuko kungu-3,00 m, khona-ke ibanga eliphakathi kwengane nesibuko li...
A. 0,75 m
B. 1,50 m
C. 2,25 m
D. 3,00 m
E. 4,50 m
Ingxoxo
Kuyaziwa:
Ukukhulisa isithombe (M) = 2
Ubude be-focal (f) = 1/2 R = 1/2 (3) = 1,5 amamitha
Kubuziwe: ibanga labantu
Impendulo:
Esibukweni esigobile, uma isithombe siqondile, ibanga lesithombe liyi-negative , okusho ukuthi isithombe sibonakala nge-virtual noma isithombe singemuva kwesibuko esigobile lapho ukukhanya kungadluli khona esithombeni.
Ifomula yokukhulisa isithunzi:
M = -s'/s
2 = -s'/s
s' = -2 imizuzwana
Bala ibanga labantu:
1/s + 1/-s' = 1/1,5
1/s + 1/-2s = 1/1,5
2/2s – 1/2s = 1/1,5
1/2s = 1/1,5
2s = (1,5)(1)
2s = 1,5
s = 1,5/2
s = 0,75 m
Impendulo efanele ngu-A.
Umthombo wombuzo:
Imibuzo yeFiziksi ye-SBMPTN