Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
SNC 2D Notes: Properties of Light How Do We See We can see objects in one of two ways: 1. By the light emitted by the object – said to be luminous 2. By the light reflected by the object – said to be non-luminous Note: Any object we can see is called a source Transmitted, Reflected and Absorbed Light can be affected in three different ways when it strikes different kinds of matter. It can be transmitted, reflected or absorbed. A substance such as air allows light to pass through it, almost as if it were not there. When light passes through a substance, it is said to be transmitted through it. Any substance that transmits light is called a medium Other substances cause light to bounce off or reflect from them. Example, mirrors, snow, white paper, etc, while other substances absorb the light that strikes them. For example black surface such as asphalt absorbs most of the light energy that strikes it. This light energy is converted into heat energy, which accounts for heating of asphalt on a sunny day. Other Properties Of Light i) Light requires no medium to travel, and thus can travel in empty space. ii) Light spreads out in all directions from the source. iii) Light travels in straight lines as long as the composition of the medium remains constant. This property of light is called linear propagation. Time Out Young One What do you think would happen if light did not travel in a continuous straight line? You can get some idea by trying to judge the position of objects under water when you look at them. Water and air are different media, and as a result of this, light changes direction as it enters and leaves the water at an angle. This results in a stick partially immersed in water appearing bent, and objects under water appearing closer to the surface than they actually are. “All right enough “chilin” back to some hardcore science” iv) Light is invisible when it travels through a vacuum or a transparent substance. Since we are unable to see light as it travels through air, we can only detect its presence by the effects it produces. v) Light reflects off of surfaces. Among other things, this gives rise to the images we see in mirrors. a) There are two types of reflection, regular and diffuse reflection. Regular Reflection: occurs when light rays strike a smooth surface and reflects in the same direction, staying parallel to one another. Diffuse Reflection: occurs when light rays reflect off a rough or uneven surface, they do not remain parallel but are scattered in different direction. vi) Light refracts, which means that it bends when passing from one medium to another. This property to light makes the straw appear bent when viewed in the water. vii) Another aspect of light that is quite common is the dispersion or breaking up of white light into its constituent colours. For example, if a beam of white light enters a glass prism, what emerges from the other side is a spread out beam of many coloured light. viii) The speed of light in vacuum has been measured to be 3.00 x 108 m/s. This is the fastest that anything has been observed to move. At that speed it would take light a mere one tenth of a second to circumvent the globe. [Scientist working on the Large Hadron Collider in Geneva Switzerland believe they have observed neutrino particles travelling faster than light. ] When light enters any material, it slows down. The amount that it slows down depends on the nature of the material. The more dense the material, the slower the speed of light. For example, in water, light is approximately 30% slower than in vacuum, while in glass it is 50% slower. In diamond, one of the most dense material known, light travels at less than 150 million meters per second.