Thin Lens Equation - AP Physics 2
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Suppose a student who was farsighted wears glasses that allows him to read at a distance of 
from his eyes to the book. His near-point distance is 
. If his glasses are 
from his eyes, what is the refractive power of his glasses lenses?
Suppose a student who was farsighted wears glasses that allows him to read at a distance of
Write the thin-lens equation.
represents the object distance from the lens, subtracting the distance between the student's eyes and the lens.
The image distance is:
Substitute the givens to the equation.
Refractive power is the inverse of focal length in 
.
Write the thin-lens equation.
The image distance is:
Substitute the givens to the equation.
Refractive power is the inverse of focal length in
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A flower is placed 
away from a converging lens. An upside down image of the flower is measured as 
tall and at a distance of 
from the lens. Find the focal length of the lens and the real height of the flower.
A flower is placed
Let the object distance be 
and the image distance be 
. The object distance is the distance the flower is from the lens. The image distance is the distance the image is located from the lens. The thin lens equation is
Alternatively you can use
To find the height, the equation for the magnification of an object is given by
it is also given as
The negative sign indicates an image that is upside down. Setting these equal gives
Let the object distance be
Alternatively you can use
To find the height, the equation for the magnification of an object is given by
it is also given as
The negative sign indicates an image that is upside down. Setting these equal gives
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You are passing a ray of light through a thin tank of alcohol to determine properties. Assume that the light ray is not effected by the tank's exterior. You find that if a piece of white paper is put underneath the alcohol tank, there is an image on the metal.
If the top of the image is 
from the center of the tank, and the top of the object is located 
from the center of the tank, what is the focal length of this lens?
You are passing a ray of light through a thin tank of alcohol to determine properties. Assume that the light ray is not effected by the tank's exterior. You find that if a piece of white paper is put underneath the alcohol tank, there is an image on the metal.
If the top of the image is
Using object distance, image distance, and focal length formula:
Where 
is object distance, 
is image distance, and 
is focal length.
Plugging everything in:
Solving for 
,
Using object distance, image distance, and focal length formula:
Where
Plugging everything in:
Solving for
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