1. PHYSICS InClass by SSL Technologies with S. Lancione Exercise-49
High School
InClass
by SSL Technologies
with S. Lancione
Exercise-49
Curved mirrors
Part 2 /2

2. Curved Mirrors PART-2 /2 and
The mirror equation is a geometrical derivation for solving
problems with curved mirrors.
Where: f = focal length (in metres)
do = Object distance (in metres)
di = Image distance (in metres)
and `
Where: M = magnification factor (no units)
hi = height of image (in metres)
ho = height of object (in metres)
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3. Curved Mirrors PART-2 Where: f = focal length (in metres)
do = Object distance (in metres)
di = Image distance (in metres)
Be sure to observe the following sign conventions when using the mirror formula:
 All distances are measured from the vertex of a curved mirror.
 Distances of objects and real images are positive.
 Distances of virtual images are negative.
 Object and image heights are positive when upright and
negative when inverted.
Parabolic mirrors are used as reflectors for searchlights, flashlights,
projectors and automobile headlights.
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4. When M is less than 1, the image is reduced.
REMEMBER
When M is less than 1, the image is reduced.
When M is negative, the image is inverted.
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5. EXERCISES

6. Question-1 Real 20 cm (in front of mirror)
An object is 60 cm from a converging mirror whose radius of
curvature is 30 cm.
Determine the characteristics of the image.
Real
Type (real or virtual): _______________
Location: _______________
Magnification: _______________
Attitude (upright/inverted): _______________
20 cm (in front of mirror)
(inverted and smaller than object)
Inverted
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7. Question-2 Real 37.5 cm (in front of mirror)
An object is 25 cm from a concave mirror whose focal length
is 15 cm. Determine the characteristics of the image.
Real
Type (real or virtual): _______________
Location: _______________
Magnification: _______________
Attitude (upright/inverted): _______________
37.5 cm (in front of mirror)
- 1.5 (inverted and larger than object)
Inverted
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8. Negative sign indicates
Question-3
An object is placed 7.5 cm from a concave mirror that has a focal
length of 15 cm. Determine the characteristics of the image.
Virtual
Type (real or virtual): _______________
Location: _______________
Magnification: _______________
Attitude (upright/inverted): _______________
15 cm (behind mirror)
2 (upright and larger than object)
Upright
Negative sign indicates
virtual image
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9. Negative sign indicates
Question-4
A converging mirror has a focal length of 15 cm. Where would
you place an object in front of this mirror in order to produce
an upright, virtual image, twice as tall as the object?
Answer
Negative sign indicates
virtual image
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10. This means a virtual image (di is negative).
Question-5
What is the focal length of a concave mirror when an object that
is placed 2 cm in front of the mirror produces an image that is
seen 5 cm behind the mirror?
This means a virtual image (di is negative).
Answer
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11. Question-6
A concave mirror has a focal length of 30 cm. A square object,
4 cm per edge, is situated with its center 10 cm in front of the
mirror. Determine:
a) The position (center) of the image.
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12. Question-6
A concave mirror has a focal length of 30 cm. A square object,
4 cm per edge, is situated with its center 10 cm in front of the
mirror. Determine:
b) The area of the image.
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13. Question-7
Illustrated below is an object situated in front of a convex mirror.
Graphically, find the image and state its characteristics. .
NOTE
Convex mirrors always produce images that are virtual, upright and reduced.
The image is virtual, upright, reduced and located behind the mirror.
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14. Question-8
An object is placed 10 cm in front of a convex mirror whose
focal length is 15 cm.
Determine the characteristics of the image.
d i
The image is virtual (since di is negative), upright (since M is positive),
smaller than the object (since M = 0.6) and located behind the
mirror.
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15. Question-9
When an object is 30 cm in front of a concave mirror, its image
is real and situated 15 cm from the mirror.
Determine the location of the image when the object is placed 6.0 cm from the mirror.
The image is virtual and
located behind mirror.
Answer
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16. Question-10
Fill in the four (4) missing quantities in the table below:
MIRROR TYPE
FOCAL LENGTH
OBJECT DISTANCE
IMAGE DISTANCE
OBJECT HEIGHT
IMAGE HEIGHT
Concave
4 cm
-12 cm
2 cm
Convex
10 cm
-7 cm
1 cm 1
3 cm 2
8 cm 3
-23.3 cm 4
0.7 cm
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17. Question-11
An object is placed in front of a convex mirror as illustrated below.
Draw and label the light rays necessary to locate the image.
Reflected ray
Incident ray
Extended ray
Incident ray
Image
Extended ray
Reflected ray
Image is virtual, upright and reduced.
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18. Question-12
An object 45.0 cm high is placed in front of a convex mirror whose focal length is 30.0 cm.
If a virtual image 15.0 cm high is formed, determine the distance the object is from the mirror.
Step-1 Calculate di
Given
A) cm
B) cm
C) cm
D) cm
E) cm
REMINDER Convex mirrors have a negative focal length. Virtual images have a negative distance.
Step-2 Calculate do
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