12.2 – Ray Diagrams with Converging Lenses
p. 495
Draw:
i. vertical line through the centre of the lens (will act as
the refraction boundary)
ii. PA = principal axis
iii. F = principal focus (on far side of lens from object)
iv. F’ = secondary focus (on side of lens closest to object)
v. O = optical centre
Draw the following rays to form an image:
Ray 1 – from top of object parallel to PA. Ray refracts thru F
(blue ray in textbook)
Ray 2 – from top of object, straight thru O. Ray does not
refract but continues straight (red ray in textbook)
Ray 3 – from top of object to lens as though ray passed thru
F’. Ray refracts parallel to PA (green ray in
textbook)
LOST every image that forms.
a)
Object between the lens and F’
L
O
S
T
b)
Object on F’
L
O
S
T
c)
Object between F’ and 2F’
L
O
S
T
d)
Object on 2F’
L
O
S
T
e)
Object beyond 2F’
L
O
S
T
12.2 – Ray Diagrams with Diverging Lenses
p. 497
Draw:
i. vertical line through the centre of the lens (will act as
the refraction boundary)
ii. PA = principal axis
iii. F = principal focus (on far side of lens from object)
iv. F’ = secondary focus (on side of lens closest to object)
v. O = optical centre
Draw the following rays to form an image:
Ray 1 – from top of object parallel to PA. Ray refracts as
though it passed thru F’ (blue ray in textbook)
Ray 2 – from top of object, straight thru O. Ray does not
refract but continues straight (red ray in textbook)
Ray 3 – from top of object to lens as though ray will pass
thru F’. Ray refracts parallel to PA (green ray in
textbook)
LOST every image that forms.
a)
Object between the lens and F’
L
O
S
T
b)
Object between F’ and 2F’
L
O
S
T
c)
Object beyond 2F’
L
O
S
T
Lens Ray Diagrams Practice
Using lined paper from your notebook, draw ray diagrams of the word problems below to see the
characteristics of the images produced.
1. A 1.8 cm tall piece of chalk is placed 6.5 cm in front of a converging lens that has a focal
length of 2.5 cm. Draw a ray diagram to locate the image of the object. Once the image is
located, state its LOST.
2. A 1.5 cm tall blade of grass is placed 8.0 cm in front of a diverging lens whose focal length is
2.5 cm. Draw a ray diagram to locate the image of the object. Once the image is located,
state its LOST.
3. A 1.25 cm insect is placed 2.1 cm in front of a converging lens that has a focal length of 3.2
cm. Draw a ray diagram to locate the image of the insect. Once the image is located, state
its LOST.
4. A 1.8 cm pencil is placed 9.5 cm in front of a diverging lens that has a focal length of 4.5 cm.
Draw a ray diagram to locate the image of the pencil. Once the image is located, state its
LOST.