REFLECTIONREFLECTION

Ray Diagram for Mirror Ray Diagram for Mirror Image & applications of Image & applications of

reflectionreflection

Lesson ObjectiveLesson Objective

To use ray diagram to determine To use ray diagram to determine image formed by plane mirror.image formed by plane mirror.

To state the application of plane To state the application of plane mirrors mirrors

To state the application of curved To state the application of curved mirrorsmirrors

Characteristics of plane Characteristics of plane mirror imagemirror image

The characteristics of plane mirror image The characteristics of plane mirror image are following:are following:

The image is uprightThe image is upright The image is of the same size as the The image is of the same size as the

objectobject The image is at the same distance The image is at the same distance

behind the mirror as the object is in behind the mirror as the object is in frontfront

The image is virtual.The image is virtual. The image is laterally inverted.The image is laterally inverted.

Why???

Image of a Point Image of a Point

Ray diagramRay diagram

p q

p=q

A virtual image of the point is formed at the position where the reflected ray appear to meet behind the mirror!

Steps to fine the image of Steps to fine the image of a pointa point Step 1: draw one Step 1: draw one

ray of light given ray of light given out by the source. out by the source.

Step 2: draw the Step 2: draw the normal and hence normal and hence the reflected ray.the reflected ray.

Step 3: extend the Step 3: extend the reflected ray in the reflected ray in the opposite direction opposite direction as it travels.as it travels.

Step 4: repeat step Step 4: repeat step 1 to 3 for a different 1 to 3 for a different of ray of light of ray of light

Step 5: find the Step 5: find the interception.interception.

At least TWO rays are needed to determine the image of one point!!!

p q

p=q

Image of an objectImage of an object

Ray diagramRay diagram Use dotted line for virtual light ray and image!

Image of an objectImage of an object

Determine how many points you Determine how many points you need to draw to fix the object. For need to draw to fix the object. For example, for an arrow, you need to example, for an arrow, you need to draw the head and the tail (two draw the head and the tail (two points) to fix the position and size of points) to fix the position and size of the arrow.the arrow.

For each point, draw its image using For each point, draw its image using TWO ray of light. TWO ray of light.

1.You will need two points to determine the position of the line segment.

2. Choose the two end points of the line segment so that you can determine the size of the image.

ExercisesExercises

Try Question 1 in your worksheet. Try Question 1 in your worksheet. (5 minutes)(5 minutes)

Application of plane Application of plane mirrorsmirrors

To look at our own imageTo look at our own image

Application of plane Application of plane mirrorsmirrors

Optical instruments such as Optical instruments such as periscope periscope

Application of plane Application of plane mirrorsmirrors

To create beautiful patterns To create beautiful patterns (Kaleidoscope)(Kaleidoscope)

Symmetry patterns created by two Symmetry patterns created by two plane mirrorsplane mirrors

Application of curved Application of curved mirrorsmirrors

Convex MirrorConvex Mirror Upright, laterally Upright, laterally

inverted, inverted, diminished, virtualdiminished, virtual

Security mirrors in Security mirrors in supermarketsupermarket

Used in sharp Used in sharp corners on roads or corners on roads or car parks to allow car parks to allow people to see people to see around blind spotsaround blind spots

Application of curved Application of curved mirrorsmirrors

Concave MirrorsConcave Mirrors Object far from the Object far from the

mirror: inverted, mirror: inverted, diminished and real diminished and real image image telescopestelescopes

Object near the Object near the mirror: upright, mirror: upright, magnified and magnified and virtual image virtual image dentist’s mirrordentist’s mirror

Other applications: Other applications: car headlamp car headlamp

DiscussionDiscussion

Discussion on Question 3 on your Discussion on Question 3 on your worksheet.worksheet.

Hints: Hints: Why can we see the image of an Why can we see the image of an

object in the mirror?object in the mirror? Consider the edge of the mirrorConsider the edge of the mirror