|Science Focus Topic 2 Notes: Reflection||| Print ||
Reflection is the process in which light strikes a surface and bounces back off that surface.
How it bounces off the surface depends on the Law of Reflection and
the type of surface it hits.
If it hits a rough surface, the light is scattered.
If it hits a smooth surface, the light reflects at an opposite angle to the angle it hits.
Light coming from a light source is called an incident ray and the light that bounces off the surface is called a reflected ray. A line that is perpendicular ( 90o with the surface) to the plane mirror is called the normal line. The angle between the incident ray and the normal line is called the angle of incidence ( i ). The angle between the reflected ray and the normal line is called the angle of reflection ( r ).
The Law of reflection states that:
the angle of incidence equals the angle of reflection
Figure 3.19 explains why an image in a mirror is the same size as the object and appears to be
the same distance from the mirror as the object. (only true for flat mirrors)
Smooth surfaces reflect light uniformly
Rough surfaces appear to reflect light randomly,
but this seemingly scattered light creates the image of the print on the page.
Reflectors help to make bicycles and cars visible at night. A reflector is made up of hundreds of tiny, flat reflecting surfaces arranged at 90o angles to one another. These small surfaces are packed side by side to make the reflector. When light strikes the reflector the light bounces off the tiny surfaces and bounces back toward the light source.
Pool players use the law of reflection to improve their game. Like a light ray, a pool ball travels
in a straight line. In a 'bank shot' (Figure 3.25, p. 199) the cue ball is bounced off the cushion at an angle
which enables the player to hit the target ball. This angle is calculated as the angle of contact (with the cushion)
is equal to the angle of impact (with the target).
Topic 2 Review p. 199