magnification 4.1 Flashcards
when does spherical ametropia occur ?
.occurs when the optical image doesn’t fall on the retina
. it is an error in image location
why do we consider image size ?
. leads to important results about blur- understand refractive error
. gives an insight into the magnification produced by different corrections ( spectacles, contact lenses , refractive surgery )- don’t produce same levels of MAG
what is the definition of transverse magnification ?
the ratio of image height to object height
what is the formula for magnification ( M ) ?
. M = L/L’ = h’/h
. this formula can be applied to any single surface or thin lens
what are the steps to calculate retinal image height ?
- calculate object location and vergence
- image vergence
- calculate magnification
- retinal image height h’=Mxh
why Retinal image heights are small and negative ?
the eye has high positive power (+60D)
Individual thin lens and/or surface magnifications can be combined to find the total transverse magnification by:?
by multiplying them
what is the power of the eye ?
+60D
what is the magnification when real objects form real image on or near the retina ?
. negative therefore image is inverted
. less than 1 therefore retinal image is much smaller than the object due to high power
how to calculate magnification for multiple surfaces/thin lenses ?
M=L1/L1’ x L2/L2’
how to calculate magnification for multiple surfaces/thin lenses ?
- object location and L1
- find L1’
- find L2= L1’/(1-dL1’)
- M=L1/L1’ X L2/L2’w
how to find retinal height for multiple surfaces / thin lenses ?
h1’/h1 = L1/L1’
h1=h2
h2’=h2 x L2/L2’
When do we use K and K’?
- specifically used when we are referring to the far point (Mr) and the retina in terms of image location.
What is an important optical principle?
Image formed by 1 surface acts asa object for 2nd.
