1. SEPTEMBER 24,2012
PHYSICS LABORATORY
ENGINEERING PHYSICSII

2. A mirror is an object with at least one polished and therefore reflective
surface. The most familiar type of mirror is the plane mirror, which has a
flat surface.
Curved mirrors are also used, to produce magnified or diminished images
or focus light or simply distort the reflected image.

3. Three Types of Mirrors
1. Plain Mirror - is a mirror with
a planar reflective surface
Note: A flat mirror reflects light rays in the same order as
they approach the mirror

4. How Plain Mirror works?
For the Plain Mirror, the light reflected according to the
Law of Reflection
When a light ray is incident upon a reflecting
surface, the angle of reflection is equal to the angle of
incidence. Both of these angles are measured relative
to a normal drawn to the surface. The incident ray, the
reflected ray, and the normal all lie in the same plane.
P.S. Reflection – bouncing back from a surface

5. Two Kinds of Reflection
 Diffuse reflection
When rays are reflected from a rough
surface, they are reflected in many directions
and no clear image is formed. None of the
normal drawn to the surface (at the point at
which the incident light ray strikes the surface)
are parallel.
 Regular reflection
When rays are reflected from a smooth
surface, they are reflected so that a clear
image is formed. The reflected rays are nearly
parallel. The normal drawn to the surface (at
the point at which the incident ray strikes the
surface) are nearly parallel.

6. When the eyes receive these light waves, it looks as if
the waves are diverging from behind the mirror, making it
appear as if the object is behind the mirror as well. This type of
image is called a VIRTUAL IMAGE, because light waves do not
actually pass through that point, it only appears so. The
distance between the object and the mirror is called the object
distance and the distance between the virtual image and the
mirror is the image distance. Notice that on plane mirrors, the
object distance is equal to the image distance.
Here’s how the REAL OBJECT and the VIRTUAL IMAGE
works..
The Formation of the Real Object & Virtual Image

7. Characteristics of a Plain Mirror
 Object size = image size
 Object distance = image distance
 Orientation = erect
 Always forms a virtual image
 Image is reversed, left to right

8. Dotted lines
Shows the
Apparent
Ray source
Angle of incidence = Angle of Reflection
For each ray

9. Three Types of Mirror
2. CONCAVE MIRROR
Concave mirrors reflect light inward to one focal
point, therefore they are used to focus light. Unlike
convex mirrors, concave mirrors show different
types of image depending on the distance between
the object and the mirror itself.
These mirrors are called "converging" because
they tend to collect light that falls on them,
refocusing parallel incoming rays toward a focus.
This is because the light is reflected at different
angles, since the normal to the surface differs with
each spot on the mirror.

10. Characteristics of Concave
Mirror
 The focal length is positive (because the object and
the focus are on the same side of the mirror)
 The object and the focus are on the same side of the
mirror (inside the arc)
 Real images can be formed by the mirror when the
object is outside of the focus; an inverted image is
formed
 Virtual images are formed by the mirror when the
object is within the focus; an erect image is formed
 No image is formed when the object is at the focus
 When the object is at the center of curvature, an
inverted image is formed at the center of curvature

11. Real
Focus
Parallel rays
Focal length = +
Forms real, inverted,
Reduced or enlarged
Reflected rays Image. Also forms
Virtual, erect,
Enlarged images.

12. Object beyond 2f
Parallel ray
2f f
Image is:
Real
Inverted
Reduced
Appears between f & 2f

13. Object at 2f Parallel ray
2f f
Image is:
Real
Inverted
Same size
Appears at 2f

14. Three Types of Mirror
3. Convex Mirror
-is a curved mirror in which the reflective
surface bulges toward the light source. Convex
mirrors reflect light outwards, therefore they are
not used to focus light.
The image is always virtual (rays haven't
actually passed though the image), diminished
(smaller), and upright . These features make
convex mirrors very useful: everything appears
smaller in the mirror, so they cover a wider field of
view than a normal plane mirror does as the
image is "compressed".

15. Characteristics of Convex
Mirror
 The focal length is negative
(because the object and the focus
are on opposite sides of the mirror)
 The object and the focus are on
opposite sides of the mirror (the
focus is on the inside of the mirror
and the object is on the outside)
 Only virtual images are formed; all
images are smaller than the object

16. Virtual focus
Dotted lines
Shows the
Apparent
Ray focus
Parallel rays
Focal length = -
Reflected rays Forms only virtual,
erect, reduced
images between
the virtual focus
and the mirror.

17. Apparent
Parallel ray Convergence of rays
(f) 2f
Image is:
Virtual
Erect
Reduced
Appears behind the
mirror

18. …the END!...