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Reflection of Light. Regular Reflection of Light. The reflection of light from smooth, shiny surfaces, such as mirrors, is called regular reflection. Light that travels towards a mirror is called the incident light. Light that is reflected from a mirror is called the reflected light .
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Regular Reflection of Light. • The reflection of light from smooth, shiny surfaces, such as mirrors, is called regular reflection. • Light that travels towards a mirror is called the incident light. • Light that is reflected from a mirror is called the reflected light.
The study of regular reflection requires measuring the angles at which the incident light strikes and the reflected line leaves the mirror. • The use of a normal is used to measure the angles from all mirror surfaces. A normal is drawn at right angles to the reflecting surface. • The angle of incidence is the angle between the incident ray and the normal. • The angle of reflection is the angle between the normal and the reflection ray.
Two Laws of Reflection • The Light Ray Model can be used to explain how light reflects from a smooth, flat surface. • The First Law of Reflection states that the angle of incidence equals the angle of reflection. • The Second Law of Reflection states that the incident ray, the refection ray and the normal are all on the same plane.
Clear vs. Diffuse Reflection Smooth, shiny surfaces have a clear reflection: Rough, dull surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions
Diffuse Reflection • Most objects that reflect light have rough, dull surfaces. What happens when parallel rays of light strike a rough surface? • Because the surface is not smooth, the light rays are scattered in many directions. This is called diffuse reflection. • The laws of reflection still apply to rough surfaces!
Most objects that you can see are non-luminous (you can see them because they reflect light to your eyes). • Most non-luminous objects have rough surfaces and will reflect light in a manner that reveals their shape, colour, and texture. • Some non-luminous objects reflect light is such a way that an image is formed. These are called mirrors. • Polished metal and calm water are also mirrors.
A flat reflecting surface is called a plane. • Plane means two dimensional surface, just like in math!
The image of an object reflected by a plane mirror appears to be at the same distance behind the mirror’s surface as the object is itself in front.
Drawing Images formed by a Plane Mirror • Draw a line representing the mirror and shade one side of it. The shade represents the reflective coating of the mirror. Draw the object in front of the mirror.
2. Draw the normals from the mirror surface to significant points, such as the top and bottom of the object. The number of other points depends on the object.
3. Measure the length of each normal drawn from the mirror to the object. Extend the normal an equal length behind the mirror surface. Complete the image by connecting the ends of the normals behind the mirror.
Application of a Plane Mirror • A Periscope! • It is an instrument in which plane mirrors are used to fold light so that the image of an object can be brought down to a lower level. • It is used for observing enemy movements from trenches without any danger of being seen. Sailors on submarines use periscopes to see things above the water level.
