Unit 2 - Optics and Light (Part 2) Flashcards
Sclera -
- the white, tougher outer wall of the eye
- keeps the eyes shape and protects its delicate internal parts
Cornea -
- transparent layer at the front of the eye
- refracts the most light, helps focus light onto retina
Iris -
- coloured part of the eye
- controls amount of light entering pupil
- makes the pupil large when light is dim
- makes pupil small when light is bright
Pupil -
- the hole in the iris
- light passes through pupil to reach retina
- can dilate (get smaller) if too much light
Lens -
- converging (convex) lens that gathers light
- helps focus light into retina
Ciliary muscles -
- controls thickness of the lens to adjust for near and far objects
- contract to make lens thicker, to see up close objects
- relax, lens is normal shape (thinner) to see far away objects
Retina -
- the area where the image is produced and converted into nerve signals
- contains light receptor cells: cone cells, to detect colour and detail and rod cells, sensitive to dim light
Fovea-
-highest concentration of cone cells
Optic nerve-
-carries nerve signals to the brain
Virtreous gel -
-clear gel (mostly water) that fills the space between the lens and the retina of the eyeball
Calculation reflection formula:
V = a N = ? C = 3.0x10(8)m/s
Calculating the formula for speed of light:
N = a V = ? C = 3.0x10(8)m/s
Differences between real and virtual images:
- Real images appear inverted, virtual images appear right
- Real images can be obtained on a screen, virtual images cannot be seen on a screen
- In case of mirrors, real image lies in front while virtual image lies behind the mirror
- In case of lenses, real image lies on the other side of the object whereas virtual image lies on the same side of the object
Real image:
Rays of light come together to make an image
Virtual image:
No rays of light at image location, it only appears that rays of light come from the image
Total internal reflection:
As light encounters a boundary between 2 media, some light reflects and some refracts.
Two conditions must be met in order for total internal reflection to happen:
- Light must be travelling from a slow to fast medium
- The angle of incidence must be more than the critical angle
Eg. Prisms used in periscopes
Medium-
Any physical substance through which energy can be transferred
Name all rays/angles in a reflection diagram , from left to right:
Incident ray, angle of incidence, the normal, angle of reflection, reflected ray
Why do objects in water appear to be at a different location than they actually are?
As light passes from one substance into another, it will travel straight through with no change of direction when crossing the boundary between the two substances. However, if the light impacts the boundary at any other angle it will be bent or refracted. As an example, if a beam of light enters water at a slight angle it will be refracted to a very small degree. If the angle of the beam is increased even farther, the light will refract with increasing proportion to the entry angle, which cause the object to be seen by the human eye in a different location.
Far-sighted:
The eye cannot refract light well enough to form an image on the retina so the image is projected farther behind the retina. This can be corrected with converging type lens.
Near-sighted:
The eye cannot refract light well enough to form an image on the retina and the image is projected farther in front of the retina compared to a healthy eye. This can be corrected with diverging type lens.
