ThreeJ

Junior Member
10+ Year Member
Jul 25, 2006
27
0
Status
Pre-Medical
hello all you potential M.D's I was wondring if one of you could clear this up for me. In the exam krackers book there is a question on optics involving the thin lens equation (1/f=1/di + 1/do). well the question gives the focal distance of 1cm and the object distance of 4cm and ask to solve for the images distance. The way I worked it out is I brought the 1/do (1/4cm) to the side the 1/f (1/1cm) was and then got a common denominator and subtracted them. This is what I did ion brackets below>

[1/1cm=1/4cm + 1/di] [1/1cm-1/4cm= 1/di] [4/4cm-1/4cm= 1/di]

[3/4cm= 1/di]. this is the answer I got yet the answer at the back of the book says it is 4/3 can anyone explain this as the book does not clearly explain it for me. :eek:

thank you
 

OCPreMed

Member
10+ Year Member
7+ Year Member
Jun 3, 2006
257
1
Los Angeles
Status
Medical Student
ThreeJ said:
hello all you potential M.D's I was wondring if one of you could clear this up for me. In the exam krackers book there is a question on optics involving the thin lens equation (1/f=1/di + 1/do). well the question gives the focal distance of 1cm and the object distance of 4cm and ask to solve for the images distance. The way I worked it out is I brought the 1/do (1/4cm) to the side the 1/f (1/1cm) was and then got a common denominator and subtracted them. This is what I did ion brackets below>

[1/1cm=1/4cm + 1/di] [1/1cm-1/4cm= 1/di] [4/4cm-1/4cm= 1/di]

[3/4cm= 1/di]. this is the answer I got yet the answer at the back of the book says it is 4/3 can anyone explain this as the book does not clearly explain it for me. :eek:

thank you
are you saying the answer says 4/3cm= 1/di or 4/3cm= di???
 
OP
ThreeJ

ThreeJ

Junior Member
10+ Year Member
Jul 25, 2006
27
0
Status
Pre-Medical
OCPreMed said:
are you saying the answer says 4/3cm= 1/di or 4/3cm= di???

Yeah it ask for di and I know my mistake now. Because I have 1/di and they ask for di I take the inverse of 1/di which converts 3/4 to 4/3 or 1.33. I just was not thinking hard enough
 
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