EDD5161A Presentation Package

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Subject PHYSICS Topic Convex lens
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Table of content

• Light refraction in Prism
• Ray diagram of a convex lens
• Ray diagram illustrating graphical construction
  rules of a convex lens
• Simulation of the ray diagram
• The six special case of convex lens
• Daily applications of convex lens

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Convex lens teaching flow chart
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Light rays passing through two prisms
QUESTION TIME
In what way do the light rays pass through the
prisms?
The light rays converge after passing through
the prisms!!
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The light rays converge!!
QUESTION TIME
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AGAIN!!! The light rays also converge to the
same point!
QUESTION TIME
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• Will the light rays still converge if we
  continue
• to cut the prisms?

YES
NO
NO
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Convex Lens

• thickest in the centre
• bends light inwards

• converging lens

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• Which of the above is/are convex lens(es)?

A C
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Terminology of Convex lens
F Focus f focal length (FC) C Optical
Center Principal axis
f focal length (FC)
Convex lens
Principal axis
f
C
F
F
C Optical Center
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Convex lens Construction Rules
? The light ray parallel to the principal axis
? The light ray through the Optical Center C
? The light ray through the focus F

passes straight through
the lens.

is refracted through the focus
F.

is refracted parallel to the principal
axis.
?
?
?
?
?
?
Now, we are going to find the image of an object
formed by a convex lens by using these rules.
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By using the three construction rules of
convex lens, draw a ray diagram of an object
with object distance u 15 cm. (Assume the
focal length of the convex lens is 10
cm.) Can you find the image distance?
Classwork
Answer
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Converging Lens Simulation
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Case 1 Object distance gt2f
When the object distance is larger than 2f , do
you know the image position?
Object
Object
Image
Image
QUESTION TIME
2F
2F
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Descriptions of the imageObject distance gt2f

• Erect / Inverted

• Erect / Inverted

• Virtual / Real

• Virtual / Real

• Magnified / Diminished /
• Same as the object

• Magnified / Diminished /
• Same as the object

• Position of image

Between the position of F and 2F on the other
side of the object.
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Case 2 Object distance 2f
Object
Object
2F
QUESTION TIME
2F
Image
Image
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Descriptions of the imageObject distance 2f

• Erect / Inverted

• Erect / Inverted

• Virtual / Real

• Virtual / Real

• Magnified / Diminished /
• Same as the object

• Magnified / Diminished /
• Same as the object

• Position of image

At the position of 2F on the other side of the
object.
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Case 3 Object distance between f and 2f
Object
Object
Image
Image
QUESTION TIME
2F
2F
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Descriptions of the imageObject distance
between f and 2f

• Erect / Inverted

• Erect / Inverted

• Virtual / Real

• Virtual / Real

• Magnified / Diminished /
• Same as the object

• Magnified / Diminished /
• Same as the object

• Position of image

Image distance gt 2f on the other side of the
object.
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Case 4 Object distance f
Where is the image?
Object
Object
2F
2F
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Descriptions of the imageObject distance f

• Position of image

Image forms at infinity.
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Case 5 Object distance lt f
Image
Image
Object
Object
QUESTION TIME
2F
2F
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Descriptions of the imageObject distance lt f

• Erect / Inverted

• Erect / Inverted

• Virtual / Real

• Virtual / Real

• Magnified / Diminished /
• Same as the object

• Magnified / Diminished /
• Same as the object

• Position of image

On the same side of the object.
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Case 6 Very large object at infinity
For a very large image at infinity
Convex lens

The light rays are nearly parallel to each other!
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Case 6 Very large object at infinity
Do you know how parallel light rays are refracted?
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Descriptions of the imageObject distance gt2f

• Erect / Inverted

• Erect / Inverted

• Virtual / Real

• Virtual / Real

• Magnified / Diminished /
• Same as the object

• Magnified / Diminished /
• Same as the object

• Position of image

Formed at the focal plane
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Descriptions of the imageObject distance gt2f

• Erect / Inverted

• Erect / Inverted

• Virtual / Real

• Virtual / Real

• Magnified / Diminished /
• Same as the object

• Magnified / Diminished /
• Same as the object

• Position of image

Formed at the focal plane
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Application of Convex lens

• Camera
• Magnifying glass

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The End
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By using the three construction rules of convex
lens, draw a ray diagram of an object with object
distance u 25 cm and height 10 cm. (Assume the
focal length of the convex lens is 10 cm.)
u 25 cm
10 cm
Object
Image
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Explanation of focal plane
Focus
Focal plane