Transcript Subject: PHYSICS Topic: Convex lens

Subject: PHYSICS
Topic: Convex lens
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
Convex lens teaching flow chart
Light Refraction in Prisms
(Revision)
Convex lens
(Converging lens)
3 construction rules
of ray diagram
Use ray diagram to illustrate
the nature of image
Daily Application
Light rays passing through two prisms
In what
doconverge
the
The
lightway
rays
light rays
passthrough
through
after
passing
the prisms!!
prisms?
the
The light rays converge!!
AGAIN!!!
The light rays
also converge to
the same point!
Will the light rays still
converge if we continue
to cut the prisms?
YES NO
Convex Lens
• thickest in the centre
• bends light inwards
converging lens
A
B
C
D
Which of the above
is/are convex lens(es)?
A&C
Terminology of Convex lens
F: Focus
f = focal length (FC)
Convex lens
f = focal length (FC)
Principal axis
f
C: Optical Center
F’
C
F
Principal axis
F: Focus
C: Optical
Center
F: Focus
Convex lens Construction Rules
straight
refracted
 The light ray through

thethe
Optical
focus
F Center
is refracted
parallel
to the

parallel to
principal
axisCispasses
throughthe
the
lens. F.
through
focus
principal
axis.



F
Now, we are going to
find the image of an
object formed by a
convex lens by using
these rules.
C
F
Classwork
Answer
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?
Converging Lens Simulation
Case 1: Object distance >2f
When the object distance is larger
than 2f , do you know the image
Object
position?
Image
2F
2F
Descriptions of the image:
Object distance >2f
• Erect / Inverted
• Virtual / Real
• Magnified / Diminished /
Same as the object
• Position of image:
Between the position of F and 2F on
the other side of the object.
Case 2: Object distance = 2f
Object
2F
2F
Image
Descriptions of the image:
Object distance = 2f
• Erect / Inverted
• Virtual / Real
• Magnified / Diminished /
Same as the object
• Position of image:
At the position of 2F on the other
side of the object.
Case 3: Object distance between f and 2f
Object
Image
2F
2F
Descriptions of the image:
Object distance between f and 2f
• Erect / Inverted
• Virtual / Real
• Magnified / Diminished /
Same as the object
• Position of image:
Image distance > 2f on the other
side of the object.
Case 4: Object distance = f
Where is the image?
Object
2F
2F
Descriptions of the image:
Object distance = f
• Position of image:
Image forms at infinity.
Case 5: Object distance < f
Image
2F
Object
2F
Descriptions of the image:
Object distance < f
• Erect / Inverted
• Virtual / Real
• Magnified / Diminished /
Same as the object
• Position of image:
On the same side of the object.
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!
Case 6: Very large object at infinity
Do you know
Remember
how parallel
the
light rays construction
are refracted?
rules of convex
lens.
F
2F
F
2F
Descriptions of the image:
Object distance >2f
• Erect / Inverted
• Virtual / Real
• Magnified / Diminished /
Same as the object
• Position of image:
Formed at the focal plane
Descriptions of the image:
Object distance >2f
• Erect / Inverted
• Virtual / Real
• Magnified / Diminished /
Same as the object
• Position of image:
Formed at the focal plane
Application of Convex lens
•Camera
•Magnifying glass
The End