The Concept of Light
Put the pieces of cardboard with the holes in a straight line.
Arrange them to a distance of about 50cm apart.
Place a lighted candle at one end of cardboard A. observe the light from behind cardboard C.
Now displace any one of the pieces of cardboard, eg. Cardboard B.
Reflection of Light
The Concept of Reflection of Light
Reflections are obtained from hard and highly polished surfaces such as mirrors and sheets of glass than from rougher surfaces, when light falls on the surface at an inclined plane angle, it is sent back into the air. This is also the case when light falls on all highly polished metals. If light falls on a polished surface at an angle 900, it is sent back into the air on the same path.
Difference between Regular and Irregular Reflection of Light
Highly polished surfaces, examples are mirror, polished cooking utensil and silvered iron sheets.
Rough surface, examples are unpolished wooden table, sheet of paper and cobblestone road.
Application of the Laws of Reflection of Light
The incident ray, the reflected ray, and the normal at the point of incidence all lies in the same plane.
The angle of incidence is equal to the angle of reflection.
Image Formed by a Plane Mirror
Describe image formed by a plane mirror
A clear image is recognised as a result of reflection of the beam striking the highly polished surfaces. This is called regular reflection.
MO is a ray of light falling on a mirror; it is called the incident ray.
OP is a ray of light leaving the mirror after reflection; it is called the reflected ray. Line NO is perpendicular to the mirror , it is called the normal.
ANGLE MON is called the angle of incidence.
(i) this is the angle between the incident ray and the normal , angle NOP is called the angle of reflection (t). this is the angle between reflected ray and the normal.