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.