European section, première
Lenses : lesson, vocabulary, exercices
I.
Basic vocabulary:
Diagram #1
Complete diagram #1with the following words:
Incident ray, refracted ray, thin converging lens,
Focal point (F’), focal length (f ’), optical center,
axis and focal plane.
Focal plane: the plane perpendicular to the lens axis
situated at a distance f ’ from the lens.
II.
Three important rays:
1.
Place the following letters on diagram #2:
Lens (L), Focal point behind the lens (F’), Focal point in front of the lens (F), optical center (O) and the axis.
Ray #1
B
Diagram #2
Ray #2
C
A
Ray #3
A ; B ; C are three object points.
2. Translate the following words and use them to describe what happens to the three rays.
to travel
to deflect
to emerge
from
to leave
to be refracted
behind
toward
to pass
to refract
parallel to
through
Ray#1:
…………..…………………………………………………………………………………………………………
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…………..…………………………………………………………………………………………………………
…………..…………………………………………………………………………………………………………
Ray#2:
…………..…………………………………………………………………………………………………………
…………..…………………………………………………………………………………………………………
Ray# :
…………..…………………………………………………………………………………………………………
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…………..…………………………………………………………………………………………………………
III.
Drawing an image:
1.
2.
On diagram #2, draw the image A’B’ of the objet AB and the image C’ of point C.
Describe the image characteristics using this 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
…………..…………………………………………………………………………………………………………
…………..…………………………………………………………………………………………………………
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09/02/2016
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IV.
Properties:
1.
2.
3.
All rays parallel to the principal axis converge to the first focal point F’.
All rays passing through the second focal point F emerging from the lens parallel to the axis.
All rays parallel to each other, but not to the principal axis, converge to the same point in the focal plane.
Using ray diagrams, illustrate these three properties in diagram #3 :
Diagram #3
F
V.
1.
F
F’
F
F’
Ray diagrams
Complete the ray diagram for the three rays emerging from the lens. Add the particular points of the lens.
L
Diagram #4
Principal
axis
O
2.
F’
Sketch the image B’ of point B, formed by the lens. Do the same with the point A.
L
Diagram #5
B
F
O
F
A
3.
On diagram #6 , sketch the image of the objet CD given by the lens L :
D
L
F
C
Document1
O
09/02/2016
Diagram #6
F
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