Fisika Study Center

physics.fisikastudycenter.com,- Learning magnifying glass or magnifier one of optical instruments. The angular magnification, image position in any eye conditions (accomodated, un accomodated and accomodated at x) will be discussed through questions and answers. This topic is learn at grade 10 high school.

Question 1

A magnifier with its focal length 5 cm is used to observe a tiny object. Find the angular magnification reached when observer eye is,
a) acccomodated
b) unaccomodated
c) acccomodated at 20 cm
assume the observer near point is 25 cm,

(Fisikastudycenter.com )

Anwer

a) an acccomodated eye
Using magnifier formula for accomodated eye


where PP = punctum proximum = near point
f = focal length

b) unaccomodated eye
Using magnifier formula for unaccomodated eyei


where PP = punctum proximum = near point
f = focal length

c) acccomodatet eye at 20 cm
Using magnifier formula for accomodated eye at X = 20 cm


where
PP = punctum proximum = near point
f = focal lenght

Question 2
An observer with his near point of 30 cm observes an object using a magnifying glass. The angular magnification reached in accomodated eye is 5, then the focal lenght of magnifyng glass equals.....cm.
Sumber soal:
Fisikastudycenter.com-Modification of UMPTN 2001

Answer
Given:
PP = 30 cm
M = 5
Accomodated eye
f = ....?



Question 3
A student observes a tiny object using magnifying glass with accomodated eye. If the object position is 10 cm and the student near point is 25 cm find:
a) the focal length
b) the power of lens
c) angular magnification reached
d) angular magnification for unaccomodated eye
Problem source :
Modifcation of UMPTN 1999-Fisikastudycenter.com

Answer
a) focal length
Data :
PP = 25 cm
S = 10 cm
Accomodated eye → the image at near point, and it's virtual image, add minus sign at S' → S' = − 25 cm
Then using lens formula:



b) the power of magnifier lens



c) the angular magnification



d) angular magnification with unaccomodated eyei



Question 4
Seorang petugas pemilu mengamati keaslian kartu suara dengan menggunakan lup berkekuatan 5 dioptri. Apabila petugas memiliki titik dekat 25 cm dan memperoleh perbesaran anguler maksimum saat menggunakan lup, tentukan jarak diletakkannya kartu suara di depan lup!
Sumber soal :
Fisikastudycenter.com-Modifikasi soal SPMB 2002

Pembahasan Soal
Finding the focal length first, then the image formed. The highest magnification is reached when accomodated eye used, that's mean the image is near point, do not forget adding minus sign.