Science 8 - Unit C - Comprehensive Notes

3.2b Myopia & Hyperopia

  • Myopia (Nearsightedness):

    • Caused by the eye being too long or a misshapen cornea.
    • Causes light to converge before the retina.
    • Objects far away appear blurry.
    • Corrected with a concave lens to diverge light before it enters the eye.

  • Hyperopia (Farsightedness):

    • Caused by the eye being too short or a misshapen cornea.
    • Causes light to converge beyond the retina.
    • Objects close up are blurry.
    • Corrected with a convex lens to converge light earlier.

3.2c Cones & Rods

  • Cones:

    • Photoreceptor cells that enable you to see color.
    • Activated by a range of the visible light spectrum.
    • Three types: blue, green, and red, each sensitive to different wavelengths of light.

  • Rods:

    • Most abundant light receptor cells in the retina.
    • Activated by low light levels.
    • Monochromatic: send only black and white images to the brain.

  • ROYGBIV:

    • Represents the colors of the rainbow: red, orange, yellow, green, blue, indigo, violet.
    • Helps to understand the colors within the visible spectrum of light.

3.3a Camera Components

  • Diaphragm:

    • Controls the size of the aperture (opening) and the amount of light let in.
    • Can adjust automatically or manually.

  • Shutter:

    • Controls the amount of time light is exposed to the sensor.
    • Opens and closes to capture the image.

  • Focusing Ring:

    • Moves the lens forwards and backwards to focus the light and form a clear image.
    • Can adjust manually or automatically.

  • Aperture:

    • The opening through which light enters the camera.

  • Light Sensors:

    • The light converges onto the light sensors.
    • A digital image is formed, and data is stored in the camera's memory.

3.3b Types of Eyes

  • Camera Eyes:

    • Eyes that have a cornea, lens, and retina and are roughly round in shape.

  • Fish Eyes:

    • Have a perfectly round lens that bulges out through the pupil.
    • Create a larger picture, allowing fish to respond to stimuli (food/predators).

  • Compound Eyes:

    • Eye made up of many small units called ommatidia.
    • Each ommatidium gives information used to create a larger picture.

  • Nocturnal Adaptations:

    • Nocturnal animals have more rods than cones in their retinas, best suiting them for seeing in the dark.

  • Ommatidium:

    • Small units in the compound eye that give information used to create a larger picture.

  • Tapetum Lucidum:

    • A layer inside the eyes of some animals (e.g., cats).
    • Acts as a mirror to reflect light inside the eye, which allows them to see better in the dark.
    • Causes "glowing eyes".

3.1 Mirrors and Lenses

  • Plane Mirror:

    • Reflecting surface with a flat, smooth, polished surface.

  • Concave Mirror vs. Lens:

    • A concave mirror reflects light convergently.
    • A concave lens refracts light divergently (bends light rays away from each other).

  • Convex Mirror vs. Lens:

    • A convex mirror reflects light divergently.
    • A convex lens refracts light convergently (bends light rays toward each other).

  • Diverge:

    • Light rays move away from each other and don't cross over one another.

  • Converge:

    • Light rays move towards each other and cross over one another at the focal point.

  • Focal Point:

    • The point that rays meet after refraction or reflection.

  • Real Image:

    • The real image is upside down and smaller (formed by a concave mirror or lens).

  • Virtual Image:

    • The virtual image is right side up and larger (formed by a concave mirror or lens).

  • Prism:

    • Transparent shape that allows light to be refracted.

  • Absorb:

    • When light strikes an object and is absorbed, the light isn't able to reflect off it (e.g., black shirt).

  • Reflect:

    • Light is bounced back (changes direction) when it hits a reflective surface (e.g., mirror).

  • Refract:

    • Bending of light rays when passing from one medium to another, changing the path of rays (e.g., pencil in a glass cup).

3.2a Eye Anatomy & Functions

  • Pupil:

    • Clear lens that directs light entering the eye toward the pupil.
    • The light enters the inside of the eye via the pupil, an opening to the eye.

  • Lens:

    • The light is focused by the lens of the eye.
    • Flexible convex lens that converges light rays.

  • Retina:

    • The light refracted by the lens forms an image on the lining of the eye (retina).
    • Contains photoreceptor cells that receive light input.

  • Ciliary Muscle:

    • Controls the shape of the lens depending on how far away the object is, so that the image formed is in focus.

  • Optic Nerve:

    • The image formed by the retina is sent to the brain as an electrical signal via the optic nerve.
    • The brain "flips" the image and decides what the object is.

  • Cornea:

    • Transparent outer layer of the eye that helps to refract light.