SCIENCE 10

Learning Activity Sheet

Quarter 2, Week 6-7

Qualitative Characteristics of Images

Prepared by: Frida A. Bantasan
Edited for MPGCHS use by: Mary Luz T. Tictica

I. Learning Competency with code

Predict the qualitative characteristics (orientation, type, and magnification) of images
formed by plane and curved mirrors and lenses. (S1 FE-llg-50)

II. Background Information

Because light travels in a straight line in one medium, a narrow beam of light, called
ray is usually represented by a straight line with an arrow head ( ) pointing to the
direction of travel.
Reflection is the bouncing off of light that strikes surfaces of objects. Refraction is the
bending of light as it passes through two different materials. When light strikes an object, the
light can be reflected, absorbed, or transmitted. Materials that reflect or absorb most of the light
that strike it are called opaque. These objects do not allow light to pass through them (ex. wood,
metal, cotton and wool fabrics). Materials that allow light to pass through them, allowing you
to see what is on the other side are transparent (clear glass, water, air). Other materials that
allow some light to pass through and are scattered are translucent. You can usually tell that
there is something behind a translucent object, but you cannot see details clearly (ex. frosted
glass, wax paper).

Types of Reflection of Light

1. Specular/Regular reflection. It is defined as light reflected from a smooth
surface at a definite angle or in one direction. This is observed in mirrors or in
still water. If you can see your reflection on a certain object, then the type of
reflection being exhibited is Specular or Regular reflection. Examples of
objects that produce regular reflection are mirrors, still water, smooth and shiny
surfaces like your phones.
2. Diffused/Irregular reflection. It is produced by rough surfaces that tend to
reflect light in all directions. If you do not see your reflection on the object, then
the type of reflection being exhibited is Diffused or Irregular reflection.
Examples of objects that produce diffused reflection are walls, clothes, chairs,
tables etc. (you do not see your face on a wooden table because the table diffuses
light rays since its surface is rough).
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 If the bundle of light rays is incident upon a smooth surface (strikes a surface), then the
light rays reflect and remain concentrated in a bundle upon leaving the surface. On the other
hand, if the surface is microscopically rough, the light rays will reflect and diffuse in many
different directions.

Reflection of Light in Mirrors

The laws of reflection states that:
1. the incident ray, the reflected ray, and the normal line to the reflecting surface
all lie in the same plane; and
2. the angle of incidence is equal to the angle of reflection.

Reflection in Plane Mirror

When light hits an opaque object with smooth surface like mirrors, light is reflected
regularly thus, an image is formed.

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 Characteristics of images formed by a plane mirror

A plane mirror is something that we use every day. If you inspect a plane mirror, you will
notice that it does not have any bulges either at the back or in front of the mirror. If it has bulges
on it, then it is considered a curved mirror (this will be discussed next).

1. Image is virtual (Light rays do not actually intersect after reflection, but they appear
to diverge from the mirror. It is behind the mirror.)
2. Same size as the object (If you are 6 feet tall, your image in a plane mirror is also 6 feet tall.
You do not see a smaller nor a bigger image of YOU in a plane mirror, right?)
3. Same orientation as the object or upright or erect
4. Same distance from the mirror as the object
5. Laterally inverted or reverse

Left-Right Reversal or Lateral Inversion

If you view an image of yourself in a plane mirror (perhaps bathroom mirror), you will
quickly notice that there is an apparent left-right reversal of the image. That is, if you raise
your left hand, you will notice that the image raises what would seem to be its right hand. If
you raise your right hand, the image raises what would seem to be its left hand. This is often
termed left-right reversal.
The letters in front of the
ambulance are written laterally. This is
because when seen in rear view mirror by
another vehicle, the image of the word
would be reversed, letting the driver read
the word properly so that he can provide
way to the ambulance.

Reflection on Curved or Spherical Mirrors

Most curved mirrors are called spherical mirrors because their shape follows the
surface of a sphere. Examples are side mirrors of vehicles and tricycles.

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Two Kinds of Spherical Mirrors:

1. The Concave or Converging Mirror

• It reflects light to the focal point thus, they are used to
focus light.
• It has a reflecting surface that is curved inward (away
from the light/user).
• Get a spoon and observe your image when you are facing
the caved in portion of the spoon. Take note of what
happens to your image. (Your face is usually upside
down).

2. The Convex or Diverging Mirror

• It’s reflective surface bulges towards the light/user.
• It reflects light outward.
• In your spoon, observe your image when you are
facing the outside portion of the spoon. Take not of
what happens to your image. (Your face is usually in
an upright orientation).

Two types of images formed by curved mirror.

Figure 7. Reflection in Concave and Convex Mirror

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 Real Image Virtual Image
1. A real image is formed when light 1. A virtual image is formed when light rays do not
rays actually meet after reflection. actually intersect after reflection, but they appear to
2. A real image can be formed on a diverge from the mirror.
screen. It is in front of the mirror just 2. A virtual image cannot be formed on a screen. It
like the object. is behind the mirror.
3. 3. A real image is inverted with 3. A virtual image is erect with respect to the object.
respect to the object.

Locating Image Formed in Curved Mirror

In locating the image formed in curved mirror graphically (ray diagrams), six important
points/terms are considered.
1) Center of Curvature, – the center of the sphere whose surface forms the curved mirror
2) Focal Point, F – where the reflected light rays meet
3) Vertex, V – the center of the mirror
4) Principal Axis – the straight line passing through the center of curvature to the vertex
5) Focal Length, – the distance from the focal point to the vertex
6) Radius of Curvature, – the distance from the vertex to the center of the curvature
Since the focal point is the midpoint of the line segment adjoining the vertex
and the center of curvature, the focal length would be one-half the radius of curvature
(C = 2f or f = C/2).

Ray diagrams are constructed in order to

determine the L•O•S•T of image formed by curved
mirrors. The L of L•O•S•T represents the relative
location.
To state the location of image or object, possible
location is divided into five general areas or
points as follows:
Case 1 – the image/object is beyond C;
Case 2 – the image/object is at C;
Case 3 – the image/object is between C and F;
Case 4 – the image/object is at F; and
Case 5 – the image/object is between F and mirror

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 The O of L•O•S•T represents the orientation (either upright or inverted). The
S of L•O•S•T represents the relative size (either magnified, reduced or the same size as the
object). And the T of L•O•S•T represents the type of image (either real or virtual).
For constructing ray diagrams, the following rules are worth noting.
Four Principal Rays in Curved Mirrors

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Example 1: The object’s location is between C and F of Concave Mirror
Note: The intersection of the reflected rays is the tip of the image and the base starts at the
principal axis.

The image is:

L – beyond C
O – inverted
S – enlarged
T – real

Example 2: The object’s location is at C of Convex Mirror

Note: Extend the reflected rays behind the mirror (using broken lines) if they do not intersect.
The image is:
L – between F and mirror
O – upright
S – reduced
T – virtual

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Refraction in Lenses
Lens is a transparent object with curved
surface/s. When light from a source traveling in
air enters the lens, it bends or changes
direction (known as refraction).
Refraction is the bending of light as it
travels from one medium to another
(from air to water) at an angle from the
normal line. Just like mirrors, lenses
form images of objects through
refraction of light.

Difference Between the Two Types of Lenses

BASIS FOR CONVEX or Converging CONCAVE or Diverging

COMPARISON LENS LENS
Meaning The lens which merges the light Concave lens can be identified
rays at a particular point, that as the lens which disperses the
travel through it. light rays that travel through it.
Figure

Curve Outward Inward

Light Converges Diverges
Center and Edges Thicker at the center, as Thinner at the center as compared
compared to its edges. to its edges.
Focal Length Positive Negative

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Image Real (behind the lens) and Virtual (in front of the lens just
Inverted image. Also produces like the object), erect and
virtual, erect and enlarged image diminished image.
in a magnifying glass.
Objects Appear closer and larger Appear smaller and farther.

Locating Image Formed in Lenses

In locating the image formed in lenses graphically (ray diagram), five important
points/terms are considered.
1) Center of Curvature, or 2F– the center of the sphere whose surface forms
the lens

2) Focal Point, F – a point where parallel light rays converge or appear to converge after
passing through the lens
3) Vertex, V / optical center, O – the geometric center of the lens
4) Principal Axis – the straight line passing through the center of curvature to the
lens
5) Focal length f - the distance from the vertex to the focal point

For constructing ray diagrams in lenses, the following rules are worth noting:

1. Any light ray traveling parallel to the principal axis is refracted by the lens through the
principal focus (P-F ray). For a convex lens, the refracted ray passes through the real
(behind) focus and for concave lens, it appears to pass through the virtual (in front) focus.

2. Any light ray that passes (for a convex lens) or appears to pass (for a concave lens)
through the principal focus is refracted by the lens parallel to the principal axis (F-P ray).

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 3. Any light ray that passes through the center of lens does not change in direction (V ray).

Example 1: The object’s location is beyond C of Convex Lens

The image is:
L – between C and F
O –inverted
S – reduced
T – real

Example 2: The object’s location is beyond C of Concave Lens

The image is:

L – between F and mirror
O – uspright
S – reduced
T – virtual

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III. Exercises/Activities
A. Below are the qualitative characteristics of images. Determine whether it is REAL
or VIRTUAL type of images. On your bubble sheet, SHADE LETTER A for
Real and SHADE LETTER B for Virtual.
1. The image is upright.
2. The image is behind the mirror.
3. The image is formed by convex mirror.
4. The image can be projected onto a screen.
5. The image is inverted with respect to the object.
6. The image is on the same side of the mirror as the object.
7. The image can be larger, smaller, or the same size as the object.
8. Reflected/refracted rays of light do not actually pass through the image.

B. Identify whether the following statements describes a plane, convex or concave mirror.
Shade the correct letter in your bubble sheet basing on the following:
A: Plane mirror B: Convex C. Concave
9. ________________forms images that are either behind the mirror or on the same
side as the object.
10. _______________forms images that are always the same distance as the object from
the mirror.
11. ________________forms images that are either smaller/same size/larger than the
object.
12. ________________ forms images that are the same size as the object.
13. ________________ forms images that are always behind the mirror.
14. ________________ forms images that are either real or virtual.
15. _________________ forms images that are upright or inverted.
16. _________________ forms images that are always reduced.
17. _________________ forms images that are always upright.
18. forms images that are always virtual.

C. Identify whether the following is CONCAVE or a CONVEX LENS. Shade LETTER

A for CONCAVE LENS and shade LETTER B for CONVEX LENS.

19. In a ________, the curve is inward.

20. ________ spread out the refracted light.
21. ________ is a converging lens.
22. ________ is thicker at the center, as compared to its edges.
23. ________is a diverging lens.
24. In ________, refracted rays meet at the focus behind the lens.
25. ________is called positive lens because of its positive focal length nature.

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IV. Closure/Reflection
“The L-O-S-T Art of Image Description in Spherical Mirrors and Lenses”
Using the ray diagrams to predict the characteristics of images formed by
curved mirrors and lenses, the following are the LOST of images.
Orientation Sized
Type
Location (upright or (same, reduced or
enlarged) (real or virtual)
Inverted)

CONCAVE MIRROR

a. Beyond the Center of Between C

Inverted Reduced Real
Curvature and F
b. Between F and Mirror Behind the
Upright Enlarged Virtual
mirror
CONVEX MIRROR

c. Between F and Between F

Upright Reduced Virtual
mirror and mirror
CONCAVE LENS

d. Between 2F and F Between F

Upright Reduced Virtual
and mirror
CONVEX LENS

e. Between 2F and F Beyond C Inverted Enlarged Real

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