Physics 1161: Lecture 21
Curved Mirrors
• Textbook sections 26-3 & 26-4
Preflight 21.1
Which ray is NOT correct?
p.a.
36% 1)
R
45% 2)
18% 3)
f
Preflight 21.1
Which ray is NOT correct?
Ray through center should reflect back on self.
p.a.
R
1)
2)
3)
f
Preflight 21.3
The image produced by a concave mirror of a real
object is:
1) Always Real
2) Always Virtual
30%
30%
3) Sometimes Real, Sometimes Virtual
39%
Where in front of a concave mirror should
you place an object so that the image is
virtual?
1.
2.
3.
4.
Close to mirror
Far from mirror
Either close or far
Not Possible
0%
1
0%
2
0%
3
0%
4
Where in front of a concave mirror should
you place an object so that the image is
virtual?
1.
2.
3.
4.
Close to mirror
Far from mirror
Either close or far
Not Possible
Solving Equations
A candle is placed 6 cm in front of a concave mirror with
focal length f=2 cm. Determine the image location.
Preflight 21.2
Compared to the candle, the image will
be:
p.a.
• Larger 29%
•
Smaller 59%
•
Same Size 12%
R
f
Solving Equations
A candle is placed 6 cm in front of a concave mirror with
focal length f=2 cm. Determine the image location.
1
1
1
 
6 cm di 2 cm
di = + 3 cm (in front of mirror)
Real Image!
Preflight 21.2
Compared to the candle, the image will
be:
p.a.
• Larger
•
Smaller
•
Same Size
R
f
3 Cases for Concave Mirrors
Upright
C
•
•
F
Object
Image
Inside F
Enlarged
Virtual
Inverted
Image
Object
C
C
•
•
Object
•
F
•
F
Image
Physics 1161: Lecture 17, Slide 9
Between C&F
Enlarged
Real
Inverted
Past C
Reduced
Real
Solving Equations
A candle is placed 6 cm in front of a convex mirror with focal length f=-3 cm. Determine
the image location.
Determine the magnification of the candle.
If the candle is 9 cm tall, how tall does the image candle appear to be?
Solving Equations
A candle is placed 6 cm in front of a convex mirror with focal length f=-3 cm. Determine
the image location.
1
1
1
 
6 cm di 3 cm
di = - 2 cm (behind mirror)
Determine the magnification of the candle.
di
-2 cm
m 
do
6 cm
Virtual Image!
m = + 1/3
If the candle is 9 cm tall, how tall does the image candle appear to be?
hi
1/ 3 
9 cm
hi = + 3 cm
Image is Upright!
Diverging
mirror!
Preflight 21.4
The image produced by a convex mirror of a
real object is ?
1) Always real
24%
2) Always virtual
61%
3) Sometimes real and sometimes virtual
15%
Mirror Summary
• Angle of incidence = Angle of Reflection
• Principal Rays
– Parallel to P.A.: Reflects through focus
– Through focus: Reflects parallel to P.A.
– Through center: Reflects back on self
• |f| = R/2
• 1 1 1
do
•

di

f
hi
di
m

ho
do