Optics Pt.2 Flashcards
What is the Mirror Equation?
1/f = 1/Do+1/Di
What is Do and Di?
Do = distance of object
Di = Distance of image
What does it mean in Di is positive? Negative?
Di is pos = Real image
Di is neg = Virtual image
What does it mean if F is neg or pos?
F (-) = Concave mirror
F(+) = Convex Mirrpr
What is the Magnification equation?
M = Hi/Ho = -Di/Do
What is Hi and Ho
Hi = Height of image
Ho = Height of Object
What does it mean if the height of the image is postitive?
If Hi/m is pos = Upright and virtual
If Hi/m is neg = Inverted/upside down and Real
What is Do always?
Positive
What does it mean if Di is positive? Negative?
Di pos = image is real
Di neg= image is virtual
Ho is always ?
Positive
What does it mean when image is upright? Inverted?
Hi is positive when upright
Hi is negative when inverted
What does it mean if light can pass through F in a convex lens? What about when it can’t in a concave?
When light can pass through F in a convex lense F is positive
When light cannot pass through F in a concave lense F is negative
In general what does + and - mean?
+ means real or upright
- means virtual or inverted
What is diverging lense lost
L - between F & O
O- upright
S- smaller
T- virtual
When object is beyond 2F in converging state lost
L - btw C and F
O- inverted
S- smaller
T- real
When object is at 2F in converging what is lost
L- at 2F
O- inverted
S- same size
T-real
Between 2F and F what is LOST converging
L- beyond 2F
O- inverted
S- bigger
T- real
At F lost converging
No image forms
Between F and O state lost converging
L- beyond 2F
O- upright
S- bigger
T- virtual
Describe a converging lense
Lense that are thickest in middle and cause incident parallel to converge thro single point after refraction
Describe diverging lenses
Thinnnest in middle and cause incident parallel light rays to spread apart after refraction
What are lenses made of
Glass and plastic
What is refraction
The bending /change of direction of light when travelling from one medium to another one
What happens when light passes into a medium that is more dense? Less?
When light passes through a medium that is more dense, it will slow down, when it passes through something less dense, it will speed up
Dense is like thicker, so water is more dense than air. Makes sense cuz passing through water will slow u down rather than air
What is the speed of light in a vacuum, water and acrylic?
Vacuum: 3.00 x 10^8 m/s
Water: 2.26 x10^8 m/s
Acrylic : 1.76 x 10^8 m/s
When does light bend away from Normal, give an example what about towards?
Light bends AWAY from normal when light goes into a less dense material, speed of light is greater. eg air
Light bends TOWARDS the normal when speed of light is less in a medium, or when a medium is more dense. Eg, water
What does fast stand for
F- faster
A-away
S-slower
T-towards
Used to describe air to water ray, Lea dense to more dense therefore bending away
As incident angle increases what happends to refraction angle
Increases
( angle is ray to normal)
What is refractive index
“N”
It is the measure of optical density, the higher the value the more optically dense it is eg zircon (1.92) is more optically dense than glycerin (1.47)
What is a critical angle?
When light refracts at 90 degrees
What’s a total internal reflection
When the incidence angle exceeds the critical angle total internal reflection happends
What are the conditions for total internal reflection
- Second medium has to be less dense and lower index of refractions. ,love from more dense to less dense
- Incident angle exceeds CA
What is lucite wrapped in and why does any life enter reflect?
Lucite is wrapped in cladding of lower index of refraction
Lucite has a very small CA,any light that enters will reflect allowing waves to travel very far
What is the CA first glass? Diamond?
Glass: 41.4, angle of incidence is always 45. Results in clear image formed
Diamond: 25 ca, sparkle comes from tir
What are the 3 seniors and describe them for TIR
- The normal one where it moves towards or away
- When the CA and TIR are equal, it refracts at 90 degrees
3.TIR, when the second medium has less density, and incident angle is bigger then CA
Cornea
Transparent front part of eye that covers iris and pupil. Together with lens and the cornea will refract light
Pupil
Hole that allows light into the eye
Iris
The eye colour, circular band of muscle that controls amount of light entering
What happens in dim and bright light
Dim - pupil dilates
Bright-pupil constricts
Retina
The inner lining at the back of the eye, contains photoreceptors which are sensitive to light images formed are inverted
Blind spot
Has no photoreceptors, cannot detect light. Optic nerve connects eye to brain
what do muscles do to focus on distant objects? Close objects?
Relax which makes lens flatter and thinner for distant objects
Muscles contract making lense thicker and rounder, to focus on close objects
Myopia
Nearsighted
Eye is too long or cornea is too curbed, image appears before Retina
Hiw to fix?
Diverging lenses spread out rays just right amount before they enter the eye so the image will converge properly onto retina
Hyperopia
Far sightedness
Eye is too short or lems is flatter, image appears behind retina
How to fix
Converging lenses converge rays just the right amount before entering eye to image will converge properly onto retina
Presbyopia
Stuff lenses become a problem with age making it difficult for cillary muscles,especially to change shape of lense
Can’t focus on nearby objects
Nearsighted person develops presbyopia, bifocals are required
Astigmatism
Irreg shaped cornea
Football shapes rather than baseball
Results in blurry vision
