Reflection of light definition
Reflection is defined as:”When light traveling in a certain medium falls on the surface of another medium,a part of it turns back in the same medium.”We see a page of a book because light reflects from each part of the page in all directions,so that some of the light rays from each part of the page enter our eye.Because almost no light is reflected by the printed words,we “see” them as black areas.
In early 1700 s,were two ideas about the nature of light;particle nature and wave nature.Newton put forward the idea of corpuscular nature of light.According to him,light consists of tiny,fast moving particles.Maxwell formulated the wave theory of light.In 1802,Thomas young proved the wave nature of light experimentally.In 1900,the Planck suggested that light consists of small packets of energy called photon was confirmed by experiments.Now we know that light has dual nature;wave as well as particle nature.
How reflection Occurs?
Reflection occurs when a light ray strikes a shiny surface(mirror) and bounces off.The ray that strikes the shiny surface is called incident ray.The ray that bounces off is called reflected ray.The point at which incident ray strikes is called point of incidence.The line perpendicular on the point of incidence is called normal.Incident ray forms angle of incidence with the normal.It is denoted by ‘i’.The angle that reflected ray forms with the normal is called angle of reflection.It is denoted by ‘r’.
Types of reflection
Nature of reflection depends on smoothness of the surface.For example,a smooth surface of silver reflects ray of light in one direction only.The reflection by these smooth surfaces is called regular reflection.
Most of the objects in everyday world are not smooth on the microscopic level.The rough surfaces of these objects reflect the rays of light in many directions.Such of reflection is called irregular reflection.
Laws of reflection of light
- Angle of incidence is equal to angle of reflection.
- Incident ray,normal ray,reflected ray at the point of incident all lie on the same plane.
Examples of reflection of light in daily life
- Reflection of light enables us to see.
- We see colours of different objects due to reflection.
- We see non luminous objects due to reflection of light.
- The number of things you see in a day is due to reflection of light.
Applications of regular and irregular reflection
Regular and irregular reflections of light have many applications in our everyday life.
- Due to the regular reflection of light we look our image in the plane mirror.
- We can turn the sunlight towards dark places by the regular reflection of light with the help of a shiny surface.
- Sunlight does not reach directly in our rooms,but we can see things in our rooms.This is because of irregular or diffused reflection of light.The light scatters in different directions when it shines on dust particles.
- We can see things just before the sunrise and just after the sunset due to the diffused reflection of light.
Reflection of light in mirrors
A shiny surface is called a mirror.A plane mirror has a smooth and flat surface.We see images in a plane mirror when light reflected by the mirror enters our eyes.We use a plane mirror to see our faces.We observe that:
- The image formed by a plane mirror is upright (straight upward).
- The image is equal in size to the object.
- The image is laterally inverted.It means your right becomes left in the image.
- The image in the plane mirror is virtual.It means the image disappears
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