European section, DNL-sciences, première
Lenses : practical work – challenge accepted
Equipment :
An optical bench
A screen
A converging lens and its support (L = +10δ)
Your brain
Read all the instructions below at first.
Challenge :
You will be divided in 6 groups, and each will have to determine the image attributes for the following position:
1. Group #1: an object located in front of the lens, at a distance smaller than f ’.
2. Group #2: an object located in front of the lens, at an exact distance of f ’.
3. Group #3: an object located in front of the lens, at a distance between f ’ and 2f ’.
4. Group #4: an object located in front of the lens, at an exact distance of 2f ’.
5. Group #5: an object located in front of the lens, at a distance bigger than 2f ’.
6. Group #6: a distant object which represent an object at infinity.
You will have to :
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perform the experiment.
use a ray diagram as precise as possible and with a scale.
calculate the position of the image using the thin lens equation.
use the magnification equation to find some image’s characteristics.
check if your analytic answers are consistent with you ray diagram.
present orally your results (ray diagram, calculation …) to your classmates and perform the experiment for them.
Consider it’s a part of a lesson, so give vocabulary (use the Internet to find it), explain and be clear …..
Your classmate will take notes, make diagrams.
During the 6 presentations, you will have to fill the following chart :
Object position
in front of the lens, at a distance smaller than f ’
in front of the lens, at an exact distance of f
in front of the lens, at a distance between f ’ and 2f ’
in front of the lens, at an exact distance of 2f ’
in front of the lens, at a distance bigger than 2f ’
a distant object which represent an object at infinity
Image characteristics
Vocabulary :
Image Characteristic
magnification
attitude
position
type
Description
same size, enlarged, diminished
erect or inverted
position from the lens, between X and Y, behind X, in front of Y….
real or virtual
Relative to : par rapport
Scale : Echelle
Vergence (symbol: L) is measured in diopter (1 D = 1 m−1).
(In some books, you can find “optical power” which is similar to vergence)
Distant, close to, at infinity ……
Bundle : faisceau
Ray diagram
Magnification : grossissement
Inward : vers l’intérieur
Document1
08/02/2016
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