Science+Notes

4/10/2012
 * In the human eye the iris which is the colourd ring functions like the diaphragm of a camera.
 * if the light is dim the iris increases the size of the eyes opening to let in more light
 * this opening is called the pupil and is the dark center of your eye.
 * the natural adjustment in the size of the pupil is called the iris reflex.
 * you are generally unaware of this reflex which is extremely rapid.
 * The daylight glare makes your eyes feel uncomfortable however the iris reflex quikly shrinks the size of the pupils making less light enter your eyes.
 * in the human eye the retina senses the light when the cells in the retina detect light they produce small electrical impulses that traval from the retina to the brain through the optic nerve

4/3/2012toc

Reflected, Refracted, Transmitted, Absorbed

 * when light travels from one medium into a denser one, for example when it moves from air into water it will bend toward the normal.
 * When light exists a denser medium its direction of travel bends away from the normal.
 * How much bending occurs depends on the type of material through which the light travels.
 * The new direction of the light is called the angle of refraction.
 * Refraction can also occur when light travels through air at different temperatures.
 * warm air is less dense then cold air.
 * Example- have you ever bin driving along a highway on a hot summer day and notice a pool of water that's a mirage. the air is close tot he ground and is hotter and less dense then the air higher up. as a result, light from the sky directed at the ground is bent upward as it enters the less dense air.

Reflection is the process by which light strikes a surface and bounces back off in the opposite angle.
 * Reflection**

light can behave in 4 ways:
 * Refraction**
 * reflected: energy "bounces off" the substance
 * absorbed: energy is retained by the substance
 * transmitted: goes thru substance at same speed
 * refracted: energy is transmitted thru substance, but at a slower speed inside substance so...light gets bent....refraction

Play with the refraction of light App: [] []

**Parts of the Eye**

 * **Iris-** like the diaphragm of a camera it controls the amount of light entering. It is the coloured part of the eye and opens and closes around a central hole to control the light entering the eye.
 * **Pupil-** this is the hole in the iris. It is like the aperture in a camera which is where the light enters.
 * **Cornea and Lens-** these cause light to converge creating a sharp image. The cornea is a transparent bulge on top of the pupil that focuses light. Light is refracted more through the cornea than the lens.
 * **Light sensitive cells-** these cells act like film in a camera, they “store” the image.
 * **Retina-**composed of rods and cones that are sensitive to light--converts light signals into electrical signals that will travel to the brain.
 * **Optic Nerve-** used to transmit the signals from the retina to the brain.

Nearsighted & Farsighted
Nearsighted: can see near objects easily, but not far objects Farsighted: can see far objects easily, but not close objects

Compare Eye and Camera
2.The iris controls the amount of light entering the eye. 3.The time of exposure of light is controlled by the eye lids || 1.A real and inverted image is formed on the photographic film. 2.The diaphragm controls the amount of light 3.The time of exposure of light is controlled by the shutter. || D**ifferences** 2.The retina retains the image only for a short time. 3. The convex lens of the eye is made of a transparent and flexible substance. || 1.The focal length of the lens cannot be changed 2.The film retains the image of the object Permanently. 3.The convex lens is made of a glass. ||
 * Similarities**
 * The Eye || The Camera ||
 * 1.A real and inverted image is formed on the retina.
 * The Eye || The Camera ||
 * 1.The focal length of the eye lens can be changed by the action of ciliary's muscles

**Accommodation**




**Dogs**
Read this: http://barkingorders.net/generalInfo/?target=85 Dogs are red-green colour blind--they only have two //cone// types rather than three. They see a brighter and less detailed world when compared to humans. Dogs have much better night vision for two reasons:
 * The have more //rods// (which enable night vision).
 * They have a structure called the //Tapetum Lucidum// - reflective surface behind the //retina// (area including the light sensitive cells) that reflects light back through it (gives the eerie shine at night).



Frequency
Frequency-number of waves for a certain amount of time Wavelength-the distance between one wave crest to the next.







Rough Reflecting Surface
Paper irregular surface. Visible light reflects diffusely from paper.

Light Pollution
Light pollution is the production of unwanted light. Modern cities have street lamps, buildings, factories and sports venues that can all release unwanted light into the sky. All of this light that is produced by the city obscures stars from view and can cause damage to ecosystems located near the city. If you have a hard time seeing stars in a city, or if a glow of light can be seen above a city when you are a distance away from it, that city is suffering from light pollution