d' (29.3)
Hinh 29.16
Thau kinh diing lam vat kinh cCia may ghi hinh (camera)
VI - CONG DUNG CUA THAU KINH
Thdu kfnh cd nhieu cdng dung hiJu feh trong ddi sdng va trong khoa hpc.
Tha'u kfnh dupc diing lam :
- Kfnh khde phuc tat ciia mdt (can, vidn, lao);
- Kinh liip ;
- May anh, may ghi hinh (camera) (Hinh 29.16);
- Kfnh hiin v i ;
- Kfnh thidn van, d'ng nhdm ; - Den chidu ;
- Mdy quang phd.
Vdi vat lieu lam thdu kfnh ngay cang hoan thien, vdi cdng nghe ehd'tao tinh vi, ngudi ta da chd'tao dupc cae dung cu quang cho dnh cd chdt lupng rdt cao.
Moi tia sang qua quang tam ciia thau kinh deu truyen thang.
Tia tdi song song vdi true cua thaiu kinh se cho tia 16 truyen qua (hay co dUdng keo dai cua tia 16 qua) tieu diem anh tren true d6.
Tia tdi (hay dUdng keo dai cua n6) qua tieu diem vat tren true se cho tia 16 song song vdi true do. Hai tieu diem vat va anh nam doi xdng vdi nhau qua quang tam.
Moi thau kinh cd hai tieu dien anh va vat la hai mat phang vuong gdc vdi true chinh va di qua cac tieu diem chinh.
f - T h a i u kinh hoi tu<=>f> 0.
Tieu eU:
0 6 tu :
Cong thdc ve thaiu kinh
f =0F' \
- T h a u kinh phan k - ;
: - V I t n anh : . + . - , d d t
- So ph6ng dai anh •^ = ~ ^ d'
CAU HOI VA BAI TAP
1. Thau kinh la gl ? Ke cac loai thau kinh.
2, Neu tinh chat quang hoc ciia quang tam, tieu diem anh, tieu diem vat. Minh hoa bang dudng truyen ciia tia sang cho m6i trudng hpp.
3. Tieu cu, do tu cua thau kinh la gl ? Don vi ciia tieu cu va do tu ?
4. Chon phat bieu dung vdi vat that dat trude thau kinh.
A. Thau kinh hoi tu ludn tao chiim tia Id hoi tu.
B. Thau kinh phan ki luon tao chiim tia Id phan ki.
C. Anh ciia vat tao bdi thau kinh khong the bang vat.
D. Ca ba phat bleu A, B, C deu sai.
5. Mpt vat sang dat trude mpt thau kinh, tren true chinh. Anh cua vat tao bdi thau kinh bang ba lan vat.
Ddi vat lai gan thau kinh mpt doan. Anh ciia vat 6 vi tri mdi van bang ba lan vat.
Co the ket luan gl ve loai thau kinh ? A. Thau kinh la hoi tu.
B. Thau kinh la phan kl.
C. Hai loai thau kinh deu phu hpp.
D. Khdng the ket luan dupc, vl gia thiet hai anh bang nhau la v6 li.
Tiep theo bai tap 5.
Cho biet doan ddi vat la 12 cm.
Tieu cy ciia thau kinh la bao nhieu ? A . - 8 cm. B. 18 cm.
C. - 20 cm. D. Mpt gia trj khac A, B, C.
Xet thau kinh hoi tu. Lay tren true chinh cdc diem / va / ' sao cho 0 / = 20F, 0/' = 20F'
(Hinh 29.17). Ve anh cua vat AB va nhan xet ve dac diem ciia anh trong m6i trudng hpp sau : - Vat that d ngoai doan 01.
- V a t that taf/.
- Vat that trong doan FI.
- Vat that trong doan OF.
F' /'
Hinh 29.17
8. Ngudi ta dung mpt thau kinh hoi tu co dp tu 1 dp de thu anh ciia Mat Trang.
a) Ve anh.
b) Tinh dudng kinh ciia anh. Cho goc trdng Mat Trang la 33'. Lay 1' ô 3.10"'* rad.
9. Vat sang AB dupc dat song song voi man va each man mpt khoang co dinh a. Mpt thau kinh hoi tu CO true chinh qua diem A va vuong goc vdi man, dupc di chuyen giua vat va man.
189
a) Ngudi ta nhan thay co mdt vi tri ciia thau kinh cho anh ro net ciia vat tren man, anh Idn hon vat. Hay chiing to rang, con mpt vi tri thii hai ciia thau kinh d trong khoang giua vat va man cung cho anh ro net ciia vat tren man.
b) Dat / la khoang each giua hai vj tri tren ciia thau kinh. Hay lap cdng thiic ciia tieu cu thau kinh f theo a va /. Suy ra mpt phuong phap do tieu cu ciia thau kinh hoi tu.
12. Trong Hinh 29.18, xy la true chinh ciia thau kinh L, A la vat diem that, A la anh ciia A tao bdi thau kinh.
Vdi moi trudng hpp, hay xac djnh ; a) A la anh that hay do.
b) Loai thau kinh.
c) Cac tieu diem chinh (bang phep ve).
A.
10. Mpt thau kinh hoi tu cd tieu cu f = 20 cm. Vat sang AB dupc dat trudc thau kinh va cd anh AB. Tim vj tri ciia vat, cho biet khoang each vat - anh la:
a) 125 cm. b)45cm.
11. Mpt thau kinh phan ki co dp tu -5 dp.
a) Tinh tieu cy cua kinh.
b) Neu vat dat each kinh 30 cm thi anh hien ra 6 dau va co so phdng dai bao nhieu ?
®
Hmh 29.18
190