If you've ever had a shiny surface like a mirror and shined light above it you will notice that once the light beam hits the surface it changes direction. This occurrence is known as reflection, when light reflects off a surface. Now the light which approaches the material is called incident ray and the light that reflects back is called the reflected ray (angle of incidence=angle of reflection). A way to symbolise this in a drawn diagram is a ray diagram. I suppose we've all stared into the mirror to see ourselves everyday so how do we see our faces in the mirror? well if your mirror is clean and shiny or polished you will get a nice and detailed picture of yourself. this is because the beams of light reflecting off the mirror and directly into your eyes causing a clear image to be seen. this type of surface is known as a specular surface. Now if you've looked into something not so smooth or clean such as a extremely wrinkled piece of aluminum foil what you will see is a distorted image of your self reflected back. This is because when light rays hit the rough surface of the aluminum foil then the light rays will reflect and scatter into different directions. This is called diffuse scattering.
So to summarise if the image is seen clearly in the surface then its a specular surface and if the image is distorted then its diffuse scattering. |
Ray diagram shows light and reflection. As you can see angle of incidence= angle of reflection (i=r)
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Light can behave incredibly when passed through another material. Remember that experiment in science where when you shine a white light through a prism, it split into colours. that is an example of refraction. through experiments we can gather that light bends as soon as it passes through another substance such as water or glass. So how does this occur? Well as soon as the light enters another substance it slows down like when we try running in water. so when it exits the material the light bends. Amazing, right? This is how things looked magnified under water, because of refraction.
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White light can be split into many different colours, because its made of different colours combined with different frequencies. you can split white light using a prism this happens as light is refracted when it enters a prism and each colour is refracted by a different amount. this process is called dispersion.
the seven colours of the spectrum are: red orange yellow green blue indigo violet This is in order of wavelength. There are a few ways to remember this. I use ROYGBIV . Here's another way Richard of York gave battle in vain. Light is composed of three primary colours : blue green and red. when all these colours combine they produce white light or they can be added to one another to produce the secondary colours: Cyan, yellow and magenta. |
picture showing dispersion of light
shows primary colours and secondary colours of light.
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Primary colours may sound familiar to you, maybe in regards with paint. Light can mix with other colours however it is different to how paint mixes. when a light hits a surface some of it is absorbed and some of it is reflected. the colour that is reflected is the colour of the object that it is reflected from. for example if you have a red apple all the colours from the spectrum is absorbed except the red which is reflected back.
so you might be asking what about things that appear to be black in white light? well they absorb all colours and reflect none. this is also the case when a coloured light shines on a object that is not the colour of the light being hone. for example a red object looks black in green light. |