Reflection-of-light 光的反射(英文版)

1、Reflection of light1You can have a view of yourself if you look intoa mirror.calm water surface.a piece of shiny metal wall.a piece of window glass.2Now 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.3Alex says, Your mirror

2、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: _.A ray of light bounces off a plane mirror.mirrorThis is an

3、example of reflection of light.1Laws of reflectionuseful words to describe the reflection of lightreflected rayincident raynormalmirrorangle of incidenceangle of reflection1Laws of reflectionLaws of reflectionVideoSimulation The incident ray,the reflected ray and the normal all lie in the same plane

4、.normalincident rayreflected raymirrornormalincident rayreflected raymirrorLaws of reflectionnormalincident rayreflected raymirror angle of incidence angle of reflection =Laws of reflectionRegular reflectionparallel incident rays parallel reflected rays on a flat, smooth surface e.g. mirror2Regular

5、and diffuse reflectionDiffuse reflectionon a rough, not perfectly smooth surface e.g. cover of a bookparallel incident rays reflected rays in different directions2Regular and diffuse reflectionQ1The angle between theThe angle between the incident ray and the _ is called the angle of incidence.normal

6、The laws of reflection state that it is equal to the angle of _.reflectionQ2The angle between anThe angle between an incident ray and the mirror is 20.The angles of incidence and reflection are _ and _. The mirror turns the ray by _ . 7070140207070Q3True or false: Reflection ofTrue of false: Reflect

7、ion of light by a rough surface does not obey the laws of reflection.(T/F)Images formed by a plane mirrorVideoRays from object O become divergent after reflection.3How a plane mirror forms an imagemirrorO I is a virtual image. cannot be picked up on a screenReflected rays appear to come from I behin

8、d the mirror.mirrorO3How a plane mirror forms an imageI by geometric constructionOIvirtual rays shown by dotted linesLocating the position of the image3How a plane mirror forms an image OIMNNM ON = NIOIThe ray diagram shows thatLocating the position of the image3How a plane mirror forms an imageLoca

9、ting the position of the image3How a plane mirror forms an imageSimulation3 virtual1 behind the mirror2 of same size as the object4 laterally inverted3How a plane mirror forms an imageProperties of the image formed by a plane mirrormirrorobjectimage3How a plane mirror forms an imageProperties of the

10、 image formed by a plane mirrorSimulationExample 1A device consists of 2 mirrors at right angles to each other.Complete the path of the ray.M145M24545The ray is turned back .parallel but opposite in directionExample 2A girl can just see her feet at the bottom edge of the mirror.Her eyes are 10 cm be

11、low the top of her head.150 m150 m(a)What is the distance between the girl and her image in the mirror?Example 2(a)Image distance = Distance = 150 2 = 300 cmObject distanceExample 2(b)How high above the floor is the bottom edge of the mirror?h12h12Example 2(b)How high above the floor is the bottom e

12、dge of the mirror?By laws of reflection, 1 = 2= 70 cmThe bottom edge of the mirror is 70 cm above the floor.h = 14012Example 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 234h1210 cmabBy laws of reflection, 3 = 4= 5 cmMinimum height of

13、 top edge of the mirrorb = a = 1012= b + 140=145 cm above the floor140 cmQ1Which of the followingWhich of the following descriptions about the image formed by a plane mirror is INCORRECT ?ALight rays come from the image to our eyes.BThe image cannot be projected on a screen.CIt is as far away from m

14、irror as the object is in front.DIt is virtual.Q2Leon 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 otherQ3True or false: If the bo

15、y.True or false: If the boy walks closer to the plane mirror, the image position of the candle will change.(T/F)Q4A 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.1.510Q5The ray diagram shows the.The ray diagram shows the extension of one of the reflected rays.Locate the image by completing the ray diagram.Q6Jenny views herself in a.Jenny views herself in a full-length mirror.(a)Construct lines from the images of Jennys feet and top of her head to her eyes.Q6Jenny views herself in a.Jenny views herself in a full