- #1
nblu
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Hi, I was reading a section which explains about the
"thin lens equation for diverging lenses" and it included an example;
Formula:
1/f = 1/di + 1/do
where f is the focal distance,
di is the distance of the image from the center and,
do is the distance of the object from the center.
Example:
f = -4cm
do = 3cm
di = ?
1/di = 1/f - 1/do
1/di = -1/4cm - 1/3cm
1/di = -3/12cm - 4/12cm
1/di = -7/12cm
1/di = -12/7cm = -1.7cm
The part where I have a confusion is colored in red.
I've been questioning, why -7/12cm was flipped in the last step.
If that example was to be solved as decimal numbers it would be;
1/di = -0.250cm^-1 - 0.333cm^-1
1/di = -1/0.583cm
then in this case, I would understand why the number has been reversed because it was ^-1
but when solving in fraction, I get confused..
Could anybody please explain for me?
Thank you in advance
"thin lens equation for diverging lenses" and it included an example;
Formula:
1/f = 1/di + 1/do
where f is the focal distance,
di is the distance of the image from the center and,
do is the distance of the object from the center.
Example:
f = -4cm
do = 3cm
di = ?
1/di = 1/f - 1/do
1/di = -1/4cm - 1/3cm
1/di = -3/12cm - 4/12cm
1/di = -7/12cm
1/di = -12/7cm = -1.7cm
The part where I have a confusion is colored in red.
I've been questioning, why -7/12cm was flipped in the last step.
If that example was to be solved as decimal numbers it would be;
1/di = -0.250cm^-1 - 0.333cm^-1
1/di = -1/0.583cm
then in this case, I would understand why the number has been reversed because it was ^-1
but when solving in fraction, I get confused..
Could anybody please explain for me?
Thank you in advance
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