Download - The Light Ray Model of Light
![Page 1: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/1.jpg)
The Light Ray Model of Light
![Page 2: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/2.jpg)
• The Light Ray Model is one of the simplest and most successful models ever developed.
• The Light Ray Model is based on a single property of light (linear motion).
• This model has played a role in the development of many optical instruments such as telescopes and cameras.
![Page 3: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/3.jpg)
• Because light travels in straight lines, the geometric principles related to straight lines can be used to show what happens to light when it strikes various objects.
• So many effects produced by light can be explained using this model, which makes up the branch of study called Geometric Optics.
![Page 4: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/4.jpg)
• To use the Light Ray Model, two terms need to be defined.
• The path taken by a fine beam of light through a medium is called a light ray.
» The light ray is represented in a diagram by a single, straight line.
» The direction of the ray of light is shown by an arrow pointing in the direction of travel.
• A group of parallel light rays is called a light beam.
![Page 5: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/5.jpg)
• A ray box is a device used to produce beams and rays of light for experiments.
![Page 6: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/6.jpg)
ShadowsShadows are places where light is “blocked”
Rays of light
Shadow
![Page 7: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/7.jpg)
• A shadow is a dark region that forms behind an object. The object is being illuminated brightly on the other side of the shadow.
• Shadows are formed when some or all of the light falling on an object is absorbed or reflected.
• Transparent and colourless substances do not produce shadows.• Translucent objects may transmit some light, but they
also absorb or reflect the striking light. • Opaque objects do not transmit any light so all of the
light is absorbed or reflected. Very dark shadows form behind opaque objects.
![Page 8: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/8.jpg)
•This figure is of a ray box and two screens. It shows a group of light rays (light beam) travelling from the box to the screens. •Although a light beam is actually made up of a large number of rays, only a few are drawn to represent the beam.
![Page 9: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/9.jpg)
•This diagram is the same as the previous diagram showing only a few light rays. •This is an even more simplified version showing only the outer limits of the beam.
![Page 10: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/10.jpg)
Umbra and Penumbra• A very dark shadow,
where there is no light is called an umbra.
• Umbra have sharply defined edges.
• There is a lighter shadow with edges that are not as sharp as an umbra, called a penumbra.
![Page 11: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/11.jpg)
Light Ray Model Explains the Formation of Shadows
• Consider the shadow produced by a point light source. The light rays are given off in all directions from the light source.
• Some of the light rays strike an opaque object and are absorbed, forming an umbra behind the object.
• The other light rays continue to travel in straight lines from the light source as they were not stopped by an opaque object.
![Page 12: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/12.jpg)
Notice that to define a shadow, it is only necessary to draw the light rays travelling from the point source to the outside edges of the opaque object . The shape of the umbra is the same as the opaque object.
![Page 13: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/13.jpg)
The size of the umbra depends on the distance between the light source and the opaque object. If the object is far from the light, a small shadow will be produced. When the object is closer to the point source, the shadow will be large.
![Page 14: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/14.jpg)
• A different kind of shadow is formed if a large light source is used. The light is no longer coming from one single point.
• The larger light sources are called extended light sources.
![Page 15: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/15.jpg)
• When an extended light source is used, the resulting shadow does not have sharply defined edges like the shadow of a point source.
• Instead, a lighter area of a shadow is formed (penumbra) because light from the extended source overlaps at the outside edges of the opaque object
![Page 16: The Light Ray Model of Light](https://reader035.vdocuments.us/reader035/viewer/2022062218/568161b8550346895dd1878f/html5/thumbnails/16.jpg)
Penumbra
Penumbra
Umbra