• Textbook sections 26-3 & 26-4

Physics 1161: Lecture 21

Curved Mirrors

R f1)

2)

3)

p.a.

Preflight 21.1

Which ray is NOT correct?

36%

45%

18%

R f1)

2)

3)

p.a.

Preflight 21.1

Ray through center should reflect back on self.

Which ray is NOT correct?

Preflight 21.3The image produced by a concave mirror of a real object is:

1) Always Real

2) Always Virtual

3) Sometimes Real, Sometimes Virtual 39%

30%

30%

Where in front of a concave mirror should you place an object so that the image is virtual?

1 2 3 4

0% 0%0%0%

1. Close to mirror2. Far from mirror 3. Either close or far4. Not Possible

Where in front of a concave mirror should you place an object so that the image is virtual?

1. Close to mirror2. Far from mirror 3. Either close or far4. Not Possible

Solving EquationsA candle is placed 6 cm in front of a concave mirror with focal length f=2 cm. Determine the image location.

R f

p.a.

Preflight 21.2Compared to the candle, the image will be:

• Larger

• Smaller

• Same Size

29%

12%

59%

Solving EquationsA 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 2 cmid di = + 3 cm (in front of mirror)

Real Image!

R f

p.a.

Preflight 21.2Compared to the candle, the image will be:

• Larger

• Smaller

• Same Size

Physics 1161: Lecture 17, Slide 9

3 Cases for Concave Mirrors

Inside F• C F• Object Image

• C F• ObjectImage

• C F• Object

Image

Between C&F

Past C

Inverted

Enlarged

Real

Upright

Enlarged

Virtual

Inverted

Reduced

Real

Solving EquationsA 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 EquationsA 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?

-2 cmm

6 cmi

o

d

d m = + 1/3

1/ 39 cm

ih hi = + 3 cm

Image is Upright!

1 1 1

6 cm 3 cmid

di = - 2 cm (behind mirror)

Virtual Image!

Diverging mirror!

Preflight 21.4The image produced by a convex mirror of a real object is ?

1) Always real

2) Always virtual

3) Sometimes real and sometimes virtual

24%

61%

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

o id d f

i i

o o

h dm

h d