REFLECTION
Characteristic of the image formed by reflection of light
The distance between the image and mirror is the same as
distance between object and mirror. The size of the image is the
same as the object. The image is virtual. The image is upright but
laterally inverted.
Question 1Diagram 1 shows a boy looking at the image of a letter
P in a mirror.
Diagram 1
How far is the image from the boy?A.4 mC.8 m
B.6 mD.10 m
Question 2Diagram 2 shows a boy standing in front of a plane
mirror.
Diagram 2
The boy moves 4 m forward.Calculate the distance between the boy
and his image.A.6 mC.10 m
B.8 mD.12 m
Question 3Diagram 3 shows a girl standing 5 m in front of a
plane mirror. The mirror is moved 1 m backwards.
Diagram 3
Calculate the distance between the initial image and her new
image.A.2 mC.12 m
B.4 mD.14 m
Question 4Diagram 4 shows a boy standing between a cat and a
mirror. The boy sees the image of the cat in the mirror. The
distance between the mirror and the boy is 1 m. The distance
between the image of the cat and the boy is 6 m.
Diagram 2
What is the distance between the boy and the cat?A.3 mC.5 m
B.4 mD.6 m
Laws of reflection
1. The incident ray, reflected ray and the normal all lie in the
same plane.2. The angle of incidence is equal to the angle of
reflection, i.e. .
Fill in the blank1.The __________ is the light ray that strikes
the surface of the mirror.
2.The __________ is the light ray the bounces off the surface of
the mirror.
3.The angle of incidence, is the angle between the __________
and the __________ ray.
4.The angle of reflection, is the angle between the __________
and the __________ ray.
5.The normal is the line that is __________ to the mirror.
Question 5
Diagram 5 shows the reflection of a light ray with an incident
angle of by a plane mirror .
Diagram 5
When the mirror is rotated clockwise through an angle of , what
is the new angle of reflection of the light ray?A.
B.
C.
D. .Question 6Diagram 6 shows a light ray being reflected by a
plane mirror.
Diagram 6
What is the angle of incidence, ?A.
B.
C.
D. .
Ray diagrams for plane mirror
A ray diagram can be drawn on plane mirrors based on the
characteristics of the image formed by plane mirrors.Step 1 :Mark
the position of the image, I and draw a straight line joining the
object, O, mirror, M and image, I.Note that the image distance, IM
is equal to the object distance, OM and the size of the image is
equal to the size of the object.
Step 2 :Draw the reflected rays from the image, I.Dotted lines
from the image to the mirror represent the virtual rays whereas
solid lines represent the reflected rays from the mirror to the
observers eye.
Step 3:Draw the incident rays from the object to the mirror.
These rays are represent by the lines joining the object to the
positions of the reflected rays on the mirror.
Complete the ray diagram below.
Choose the correct answerThe characteristics of the image formed
by a plane mirror are
same size as the objectsmaller than the size of the objectbigger
than the size of the object
object distance > image distanceobject distance < image
distanceobject distance = image distance
UprightInvertedLaterally inverted
real imagevirtual imageno image
Ray diagrams for concave mirror (1)
There are three basic rays that need to be drawn in drawing ray
diagrams for concave mirror.
Incident rayReflection ray
A ray parallel to the principal axisreflected through F
A ray through Freflected parallel to the principal axis
A ray through Creflected along the original path
Ray diagrams for concave mirror (2)
The characteristic of image formed by a concave mirror based on
different positions of an object.
Position of objectRay diagramPosition of image and
characteristic of image
Object, O is between F and P.
Object, O is at F
Object, O is between F and C
Ray diagrams for concave mirror (3)
The characteristic of image formed by a concave mirror based on
different positions of an object.
Position of objectRay diagramPosition of image and
characteristic of image
Object, O is at C
Object, O is beyond C
Object is at infinity
Ray diagrams for convex mirror (1)
There are three basic rays that need to be drawn in drawing ray
diagrams for convex mirror.
Incident rayReflection ray
A ray parallel to the principal axisreflected as if it comes
from F
A ray through Freflected parallel to the principal axis
A ray through Creflected along the original path
Ray diagrams for convex mirror (2)
The characteristic of the image by a convex mirror are the same
for different positions of the object.
Position of objectRay diagramPosition of image and
characteristic of image
Object, O is between F and P
Object, O is beyond F
Refraction
Match column A to column B correctly Column AColumn B
Refraction of light
Snells law states that
Refraction index of medium, can be expressed asthe bending of a
light ray when the light ray travels from one medium to another
medium
For a given transparent medium, refractive index can be
expressed as
Refractive index in terms of and iswhen light travels from air
into another medium, the ratio is constant.
The angle between the incident ray and the normal is theangle of
refraction
The angle between the refracted ray and the normal is the angle
of incidence
Laws of refraction
1. The incident ray, refracted ray and the normal all lie in the
same plane.2.
The ratio is a constant, where is the angle of incidence and is
the angle of refraction.
Label the diagram below which show how light rays refract when
passing through air to glass and glass to air.
Normal angle of incidence, angle of refraction, incident ray
refracted ray
Complete the diagram below which describe ways in which a light
ray is refracted when it travels to a medium of different optical
density.
Light travels from an optically less dense medium to an
optically denser medium
The light ray is refracted __________ the normal. The speed of
light __________ .
Light travels from an optically denser medium to an optically
less dense medium
The light ray is refracted __________ from normal. The speed of
light __________ .
Light travels through two medium of different optical densities
perpendicularly
The light ray does not __________ its direction. The speed of
light __________ .
Refractive index
1. For light rays entering a medium from vacuum, the refractive
index, for the medium is expressed as
Question 7The figure below shows a light ray passing through a
plastic block.
The refractive index of the plastic block is 1.24, find(a) the
speed of light in the plastic block(b) the angle of refraction
[speed of light, ]
Question 8
In diagram below, a thick line is drawn on a piece of white
paper. A glass block of a thickness of is placed on it. The line
seemed to rise by .
What is the refractive index of the glass?
Complete the ray diagram for the following situation
Total Internal Reflection
1. Total internal reflection is the reflection of the total
amount of incident light rays at the boundary between two mediums
of different optical densities.2. Total internal reflection can
only occur when(a) light rays travel from an optically denser
medium to a less dense medium, and(b) the angle of incidence is
greater than the critical angle.
Draw the ray diagram for the following situationCondition
Diagram
Description Light ray is refracted away from the normal A weak
reflected ray is produced Increasing the angle of incidence will
increase the angle of refraction and produce a reflected ray with
increasing intensity.
Light ray is refracted along the boundary between the two
mediums. A stronger reflected ray can be seen as a weak refracted
ray travels along the boundary. Light ray is no longer refracted
but is totally internally reflected. Hence, a refracted ray cannot
be seen at all. Total internal reflection is said to have
occur.
Answer the following question.1.
When the angle of incidence, is the critical angle, , the angle
of refraction, is .
Derive the formula for critical angle, .
2. The critical angle of a glass is . If a light ray travels
from the glass to air,(a) state the phenomenon that will happen if
the angle of incidence is(i) : _______________________(ii) :
_______________________(iii) : _______________________(b) determine
the refractive index of the glass
3. Given that the critical angle of glass is , complete the
following diagrams to show the path of each ray after it strikes
the prism.