What is light all about?

Answer 1

When light moves it moves at the amazing speed of 186, 000 mi/sec. However, when light hits a glass block it slows down as glass is a denser substance (light slows down once it enters a denser substance to the one it was traveling through before [air]). The rays that enter the glass first slow down first pulling the other rays closer to normal. Once those rays leave the glass block they pull the rest of the ray away from normal again as they speed up. They speed up as they are now entering air a less dense substance than glass. The angle the light enters at is called the angle of incidence, the angle that the light enters at and leaves at are the same. (See fig. 1A and fig. 1B)

Once a ray of white light enters a triangular prism the light splits into it's spectral components, the colours of the rainbow; Red, Orange, Yellow, Green, Blue, Indigo, Violet. This is dispersion. The source of light could be the sun or in an experiment a ray box. Dispersion happens because of the different wavelengths of white light refract at different amounts depending on the colour, red is refracted the least as it has the longest wavelength so it slows down less and is out of the spectrum first, violet gets refracted the most (The difference between the colours is only milliseconds). As in a prism the colours are refracted at different amounts instead of the rays that enter first dragging the rest the colours refract at different amounts and take different paths allowing us to see them. We know this because if you shine a ray of white light through a triangular prism you can see the spectrum of light leave it

If a ray of light is shone on a flat mirror it is reflected back. The incidence ray is reflected because mirrors are opaque and not transparent so the light can't travel through it. The angle of reflation (the reflected ray) will be the same as the angle of incidence, and because all the light is reflected exactly back you can see your reflection in the mirror. The mirror does not have to be flat though it can be curved. A concave mirror curves inwards magnifying images because it collects parallel light rays and reflects them through a principle focus. A convex mirror a wider range of the image is shown. It reflects the rays so they look like they come from behind.

Reflection is when waves bounce of a surface and travels onward at the same angle but in a different direction; all reflection follows the law of reflection to some point, the law of reflection being that the angle of incidence being the same as the angle of reflection. Refraction on the other hand is the change in the direction of light due to a change in the density of the object it is traveling through causing a change in it's speed. Dispersion, however, is splitting light up into its spectral components. Reflection bouncing light, Refraction changing it's speed and direction, and dispersion splitting it up.

It may be common knowledge that mirrors are used in magic shows (Pepper's ghost) and circuses (hall of mirrors); that glass blocks are used to demonstrate refraction and dispersion helpful to jewellers making diamonds and other precious stones look more impressive- and that they can all be used in theatre. But there are some other uses that are not so common; the prismatic compass makes uses a small capsule that is filled with oil and a magnetized dial. This combination is amplified with an illumination element that helps one of the most accurate compass readings. Prisms are also used in eyeglasses, they are used mainly for double vision, positional correction, or convergence correction.

There are novelty mirrors (MP3 mirror, interactive mirrors, Tetris mirrors and more.) and even an Ironing board mirror made by Aïssa Logerot. Apollo 11 left a mirror on the moon; it is used to reflect laser light from Earth, and with our knowledge of light we can measure the distance from the Earth to the moon by measuring the round-trip time of the light. We now know that the moon is slowly moving away from the Earth. Mirrors can be used to shine a spot of sunlight far away (you reflect the light away from you in the direction you want), and communicate with flashes of light to others if you are out in the wilderness hiking, or even start a fire. And scientists recently discovered a fish that uses its mirrored eyes and lenses to find its way 500-2,500 metres below sea level. It is called the "Brownsnout spookfish".

Glass blocks can be used in decoration to make all sorts of adornments to hang around buildings. They can also be used as fire protection.

--------------------------------------------------

I handed this in as Science H/W so please do not copy and paste the whole thing.