1. REFLECTION Ray Diagram for Mirror Image & applications of reflection

2. Lesson Objective To use ray diagram to determine image formed by plane mirror. To use ray diagram to determine image formed by plane mirror. To state the application of plane mirrors To state the application of plane mirrors To state the application of curved mirrors To state the application of curved mirrors

3. Characteristics of plane mirror image The characteristics of plane mirror image are following: The image is upright The image is upright The image is of the same size as the object The image is of the same size as the object The image is at the same distance behind the mirror as the object is in front The image is at the same distance behind the mirror as the object is in front The image is virtual. The image is virtual. The image is laterally inverted. The image is laterally inverted. Why???

4. Image of a Point Ray diagram Ray diagram pq p=q A virtual image of the point is formed at the position where the reflected ray appear to meet behind the mirror!

5. Steps to fine the image of a point Step 1: draw one ray of light given out by the source. Step 1: draw one ray of light given out by the source. Step 2: draw the normal and hence the reflected ray. Step 2: draw the normal and hence the reflected ray. Step 3: extend the reflected ray in the opposite direction as it travels. Step 3: extend the reflected ray in the opposite direction as it travels. Step 4: repeat step 1 to 3 for a different of ray of light Step 4: repeat step 1 to 3 for a different of ray of light Step 5: find the interception. Step 5: find the interception. At least TWO rays are needed to determine the image of one point!!! pq p=q

6. Image of an object Ray diagram Ray diagram Use dotted line for virtual light ray and image!

7. Image of an object Determine how many points you need to draw to fix the object. For example, for an arrow, you need to draw the head and the tail (two points) to fix the position and size of the arrow. Determine how many points you need to draw to fix the object. For example, for an arrow, you need to draw the head and the tail (two points) to fix the position and size of the arrow. For each point, draw its image using TWO ray of light. For each point, draw its image using 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.

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

9. Application of plane mirrors To look at our own image To look at our own image

10. Application of plane mirrors Optical instruments such as periscope Optical instruments such as periscope

11. Application of plane mirrors To create beautiful patterns (Kaleidoscope) To create beautiful patterns (Kaleidoscope) Symmetry patterns created by two plane mirrors Symmetry patterns created by two plane mirrors

12. Application of curved mirrors Convex Mirror Convex Mirror Upright, laterally inverted, diminished, virtual Upright, laterally inverted, diminished, virtual Security mirrors in supermarket Security mirrors in supermarket Used in sharp corners on roads or car parks to allow people to see around blind spots Used in sharp corners on roads or car parks to allow people to see around blind spots

13. Application of curved mirrors Concave Mirrors Concave Mirrors Object far from the mirror: inverted, diminished and real image  telescopes Object far from the mirror: inverted, diminished and real image  telescopes Object near the mirror: upright, magnified and virtual image  dentist’s mirror Object near the mirror: upright, magnified and virtual image  dentist’s mirror Other applications: car headlamp Other applications: car headlamp

15. Discussion Discussion on Question 3 on your worksheet. Discussion on Question 3 on your worksheet. Hints: Hints: Why can we see the image of an object in the mirror? Why can we see the image of an object in the mirror? Consider the edge of the mirror Consider the edge of the mirror