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Physics - Light
Physics Definitions
| Term | Definition |
|---|---|
| Reflection | The bouncing of light off an object |
| Laws of Reflection | 1 - The incident ray, the normal & the reflected ray all lie on the same plane. 2 - The angle of incidence is equal to the angle of reflection. |
| Virtual image | A virtual image is an image formed by the apparent intersection of rays This image cannot be projected onto a screen. |
| Reflection - A ray which strikes the pole of a concave mirror | Is reflected at an equal angle |
| Reflection - A ray which passes through the centre of curvature of a concave mirror | Is reflected back along its own path |
| Reflection - A ray which comes in parallel to the axis of a concave mirror | Is reflected back through the focus (f) |
| Reflection - A ray which passes through the focus of a concave mirror | Is reflected parallel to the axis. |
| Real image | A real image is formed by the actual intersection of light rays. This image can be located on a screen. |
| Reflection - Formula for a real/virtual image | Real - 1/u + 1/v = 1/f Virtual - 1/u - 1/v = 1/f |
| Reflection - A ray which strikes the pole of a convex mirror | Is reflected at an equal angle |
| Reflection - A ray which is heading for the centre of curvature of a convex mirror | Is reflected back along its own path |
| Reflection - A ray which enters parallel to the axis of a convex mirror | Is reflected as if it came from the focus. |
| Reflection - A ray which is heading for the focus of a convex mirror | Is reflected out parallel to the axis. |
| Rules for a convex mirror | The image is always virtual and always diminished. |
| Uses for a concave mirror | For a dentist or for a torch |
| Uses for a convex mirror | Door mirror of a car, in shops to deter shoplifters & to show a view of oncoming traffic |
| What is Refraction? | The bending of light when it goes from one medium to another |
| Rules for refraction | When light goes from rarer to denser, it is refracted towards the normal. When it goes from the denser to rare, it is refracted away from the normal. |
| Laws of Refraction | 1) The incident ray, normal and the refracted ray all lie on the same plane. 2) Snell's law is sin i / sin r = n (the refractive index) |
| What is the refractive index of a medium | The ratio of the sine of angle i to the sine of the angle r when light travels from a vacuum into that medium |
| Formula for depth | n = Real depth/ apparent depth |
| What is the critical angle? | When light travels from a denser to a rarer medium, the angle of incidence whose corresponding angle of refraction is 90 is called the Critical Angle. |
| What is total internal reflection? | When light going from a denser to a rare medium has an angle of incidence that is greater than the critical angle, it does not enter the second medium. It is all reflected back in the denser medium. |
| How do you find the refractive index using C | n = 1/sin C |
| What is an optical fibre? | A very thin transparent rod (usually made of glass) which light can travel via total internal reflection. |
| Uses for optical fibres | There is much less energy loss, they are much smaller than electric wires and there is less interference. |
| A ray which strikes the optic centre of a convex lens | Goes straight through the lens |
| A ray which strikes the convex lens while travelling parallel | Passes through the focus on the other side of the lens. |
| A ray which passes through the focus and then strikes the convex lens | Emerges parallel to the axis |
| Rules for a convex lens | If the object is outside the focus, the image is real and inverted. If the object is inside the focus, the image is virtual and upright. |
| Formula for a convex lens | 1/u + 1/v = 1/f |
| A ray which is heading for the focus beyond a concave lens | Emerges parallel to the axis. |
| A ray which strikes the concave lens parallel | Is refracted as if it came from the focus. |
| Rules for a concave lens | The image is always virtual and upright when outside of f. The image is always diminished when inside of f. |
| Formula for power of a lens | P = 1/f |
| What is short sightedness | Short sightedness is when you cannot bring distant objects into focus, also known as myopia. |
Created by:
JoeBrennan2020
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