Also see Simulation program 1.1 in Physics at Work Multimedia CD-ROM 1.
Also see Simulation program 1.3 in Physics at Work Multimedia CD-ROM 1.
روعه Exellent P P Reflection Of Light
Reflection of light
1 You can have a view of yourself if you look into a mirror. calm water surface. a piece of shiny metal wall. a piece of window glass.
2 Now you look into a mirror and see the image of yourself. In front of the mirror. On the surface of the mirror. Behind the mirror.
3 Alex says, ‘Your mirror image is smaller than yourself’. Do you agree? Yes, the image is really smaller. No, your image and you are always of the same size. It looks smaller just because it is far from you. No, it depends on how far you stand from the mirror. Others: ________.
<ul><li>A ray of light bounces off a plane mirror. </li></ul>1 Laws of reflection This is an example of reflection of light. mirror
<ul><li>useful words to describe the reflection of light </li></ul>1 Laws of reflection reflected ray incident ray normal angle of incidence angle of reflection mirror
2 Regular and diffuse reflection Diffuse reflection <ul><li>on a rough, not perfectly smooth surface </li></ul><ul><li>e.g. cover of a book </li></ul>parallel incident rays reflected rays in different directions
Q1 The angle between the… The angle between the incident ray and the _______ is called the angle of incidence. normal The laws of reflection state that it is equal to the angle of ___________. reflection
Q2 The angle between an… The angle between an incident ray and the mirror is 20 . The angles of incidence and reflection are ____ and ____ . The mirror turns the ray by ____ . 70 70 140 70 70 20
Q3 True or false: Reflection of… True of false: Reflection of light by a rough surface does not obey the laws of reflection. (T/F)
<ul><li>Rays from object O become divergent after reflection. </li></ul>3 How a plane mirror forms an image mirror O
3 How a plane mirror forms an image <ul><li>I is a virtual image . </li></ul><ul><li>cannot be picked up on a screen </li></ul>Reflected rays appear to come from I behind the mirror. mirror O I
Locating the position of the image <ul><li>by geometric construction </li></ul>virtual rays shown by dotted lines 3 How a plane mirror forms an image O I
3 How a plane mirror forms an image <ul><li>OI ⊥ MN </li></ul>N M <ul><li>ON = NI </li></ul>The ray diagram shows that Locating the position of the image O I
Locating the position of the image 3 How a plane mirror forms an image Simulation
3 How a plane mirror forms an image 3 virtual 1 behind the mirror 2 of same size as the object 4 laterally inverted Properties of the image formed by a plane mirror mirror object image
3 How a plane mirror forms an image Properties of the image formed by a plane mirror Simulation
Example 1 A device consists of 2 mirrors at right angles to each other. Complete the path of the ray. 45 The ray is turned back . parallel but opposite in direction M 1 45 M 2 45
Example 2 A girl can just see her feet at the bottom edge of the mirror. Her eyes are 10 cm below the top of her head. (a) What is the distance between the girl and her image in the mirror? 150 m 150 m
Example 2 (a) Image distance = Distance = 150 2 = 300 cm Object distance
Example 2 (b) How high above the floor is the bottom edge of the mirror? 1 2 h
Example 2 (b) How high above the floor is the bottom edge of the mirror? By laws of reflection, 1 = 2 = 70 cm The bottom edge of the mirror is 70 cm above the floor. h 1 2 h = 140 1 2
Example 2 (c) What is the minimum height of the top edge of the mirror if she is able to see the top of her head?
Example 2 By laws of reflection, 3 = 4 = 5 cm Minimum height of top edge of the mirror = b + 140 =145 cm above the floor 3 4 h 1 2 10 cm a b b = a = 10 1 2 140 cm
Q1 Which of the following… Which of the following descriptions about the image formed by a plane mirror is INCORRECT ? A Light rays come from the image to our eyes. B The image cannot be projected on a screen. C It is as far away from mirror as the object is in front. D It is virtual.
Q2 Leon and Partick look in a... Leon and Patrick look in a plane mirror placed directly in front of Leon. Can they see themselves and each other in the mirror? Leon can see himself but Patrick cannot. Both of them can see each other
Q3 True or false: If the boy... True or false: If the boy walks closer to the plane mirror, the image position of the candle will change. (T/F)
Q4 A boy of height 1.5 m stands... A boy of height 1.5 m stands 5 m in front of a plane mirror. His image is ______ m tall and ______ m from him. 1.5 10
Q5 The ray diagram shows the... The ray diagram shows the extension of one of the reflected rays. Locate the image by completing the ray diagram.
Q6 Jenny views herself in a... Jenny views herself in a full-length mirror. (a) Construct lines from the images of Jenny’s feet and top of her head to her eyes .
Q6 Jenny views herself in a... Jenny views herself in a full-length mirror. (b) Mark on the mirror to indicate minimum region Jenny uses to see her full image.
Q6 Jenny views herself in a... (c) Does this region of the mirror depend on Jenny’s distance from the mirror? (Yes/No) Jenny views herself in a full-length mirror.