(easy) Finding variables with mirror equation

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The discussion revolves around a district assessment involving two lenses and the calculation of total magnification. The first lens has a focal length of 1.2 cm, and the object is placed 1.3 cm away, resulting in a magnification of 12x. The second lens, with a focal length of 0.42 cm, uses the image from the first lens as its object, leading to confusion in calculations. The participant initially calculated a total magnification of 0.3x, while peers reported values in the 200s, indicating a misunderstanding of the lens system. The clarification that the image from the first lens serves as the object for the second lens significantly aids in resolving the confusion.
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This isn't exactly a homework problem, per se, but this was a district assessment I already took today. I was confident that I would get a good grade, but it turns out I got a measly 65%. I don't remember the exact wording, but I do remember the general idea of it.

Homework Statement


There are two lenses, both of which are 16cm apart. An object is 1.3cm away from the first lens.

First lens
f = 1.2cm
do = ?
di = ?
M = ?

Second lens
f = .42cm
do = ?
di = ?
M = ?

Total Magnification
Mtot = ?

Homework Equations


di = dof/do-f
M = di/do
Mtot = M1*M2

The Attempt at a Solution


First lens
f = 1.2cm
do = 1.3cm (given)
di = 15.6 cm
M = 12x

Second lens
f = .42
do = 16cm+1.3cm = 17.3cm
di = .43 cm
M = .025x

Total Magnification
Mtot = .3x
Looking back at it now, I think I messed up somewhere in the second lens.
I've asked friends what they got for Mtot, and the majority of them said a number around the 200s.

What am I doing wrong?
 
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classi said:
This isn't exactly a homework problem, per se, but this was a district assessment I already took today. I was confident that I would get a good grade, but it turns out I got a measly 65%. I don't remember the exact wording, but I do remember the general idea of it.

Homework Statement


There are two lenses, both of which are 16cm apart. An object is 1.3cm away from the first lens.

First lens
f = 1.2cm

Second lens
f = .42cm

Total Magnification
Mtot = ?

Homework Equations


di = dof/do-f
M = di/do
Mtot = M1*M2

The Attempt at a Solution


First lens
f = 1.2cm
do = 1.3cm (given)
di = 15.6 cm
M = 12x

Second lens
f = .42
do = 16cm+1.3cm = 17.3cm
di = .43 cm
M = .025x

Total Magnification
Mtot = .3x

Looking back at it now, I think I messed up somewhere in the second lens.
I've asked friends what they got for Mtot, and the majority of them said a number around the 200s.

What am I doing wrong?
Hello classi. Welcome to PF !

The image formed by the first lens becomes the object for the second lens.
 
Oh my gosh, thanks! :)
That makes perfect sense; I don't know why I didn't think of that before.
 
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