1、Reflection of light,1You can have a view of yourself if you look into,What will happen if a ray approaches a mirror?,when light hits a surface usually some of the light is reflected!,A ray of light bounces off a plane mirror.,This is an example of reflection of light.,1Laws of reflection,useful word
2、s to describe the reflection of light,reflected ray,incident ray,normal,angle of incidence,angle of reflection,1Laws of reflection,The incident ray,the reflected ray,and the normal,all lie in the same plane.,Laws of reflection,angle of incidence,angle of reflection,=,Laws of reflection,The normal is
3、 the line drawn perpendicular(垂直的)to the surface at the point where the light ray touches the surface.过入射点垂直于入射平面的直线叫做法线.The angle of incidence (i) is the angle between the incident ray and its normal. 入射光线与法线间的夹角.The angle of reflection（r）is the angle between the reflected ray and its normal.入射光线与法
4、线间的夹角.,QWhich of the following,Which 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 mirror as the object is in front.,DIt is virtual.,Regular reflec
5、tion,parallel incident rays,parallel reflected rays,on a flat, smooth surface,e.g. mirror,2Regular and diffuse reflection,QThe 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,
6、Rays from object O become divergent after reflection.,3How a plane mirror forms an image,mirror,O,I is a virtual image.,cannot be picked up on a screen,Reflected rays appear to come from I behind the mirror.,mirror,O,3How a plane mirror forms an image,QTrue or false: Reflection of,True of false: Ref
7、lection of light by a rough surface does not obey the laws of reflection.,(T/F),Diffuse reflection,on a rough, not perfectly smooth surface,e.g. cover of a book,parallel incident rays,reflected rays in different directions,2Regular and diffuse reflection,小结,反射定律：当光发生反射时，入射光线、法线、反射光线在同一平面内入射光线、反射光线分居
8、在法线两侧、入射角等于反射角。应用反射定律，画光路图。反射分为镜面反射和漫反射，它们都遵循反射定律。,Exercise,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,Homework,1. Do the exercise in the exercise books related light reflection.2. Since we have learned the reflection, please think about why we can observe the light objects.,
