Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
28 Cards in this Set
- Front
- Back
|
What is the base curve of a lens?
|
The front or outside curve of an optical lens. The convex side.
Page 25 |
|
|
What is the ocular curve of a lens?
|
The inside or back curve of an optical lens. The concave side.
Page 25 |
|
|
What is Diopter?
|
The unit of lens power. Also called focal power or vertex power. At 1 diopter there is a focal length of 1 meter.
Page 25 |
|
|
How can we measure the diopter of a lens?
|
Lensometer is an instrument that measures the power of a lens.
Page 25 |
|
|
What is the characteristic of the optical center?
|
The point of no refraction on the lens. There is no prismatic effect.
|
|
|
Write the characteristics of the plus lens?
|
-It is thickest at the center.
-Made up of two prisms base to base. -Optic center is at the base. -Focal point behind the lens. -Converges light. -Magnifies. -Creates real image -Corrects hyperopia. -Increases power as increasing distance from eye. -Against the motion. -Inverted image Page 33 & 34 |
|
|
Write the characteristics of the minus lens?
|
-Thickest at the edges.
-Base curve has longer radius than the ocular curve. -Made up of two prisms apex to apex. -Optic center at apex. -Virtual focal point in front of lens. -Diverges light. - Minifies. -Creates virtual image. -Corrects myopia. -Lengthens focal point to cornea. -With the motion. Page 35 & 36 |
|
|
The power of a lens depends on:
|
-Diopter value/ value of the curves
-Refractive index of the optical material -Thickness of the lens. -Vertex distance Page 26 |
|
|
What does a prism do to the light?
|
Deviates light toward the base, disperses the white light into its component colors, and displaces the object toward the apex.
Page 23 |
|
|
If the focal length of a lens increases, the power of the lens will (increase/decrease).
|
If the focal length of a lens increases, the power of the lens will <decrease>.
|
|
|
If the radius of a lens increases, the focal length of the lens will (increase/decrease).
|
If the radius of a lens increases, the focal length of the lens will <decrease>.
|
|
|
If the radius of a curve increases, the focal length of the lens will ......... and the power of the lens will .......... .
|
If the radius of a curve increases, the focal length of the lens will <increase> and the power of the lens will <decrease>.
|
|
|
Increasing the refractive index ......... the power. (increases/decreases)
|
Increasing the refractive index <decreases> the power.
|
|
|
Cornea acts as a ..... lens. (plus/minus)
|
Cornea acts as a <plus> lens.
|
|
|
Calculate the focal length of this lens.
0.50 D |
|
|
|
Calculate the power of these lenses:
1) FL 10". 2) FL 80" 3) FL 5". 4) FL 20" 5) FL 8" 6) FL 100mm. 7) FL 250mm 8) FL 1000mm. 9) FL 125 mm 10) FL 50 mm 11) 4 m. 12) 1/2 m 13) 2 m. 14) 0.2 m 15) 1 m 16) 50 cm. 17) 200 cm 18) 25 cm. 19) 5 cm |
1) 4.00 D. 2) 0.50 D. 3) 8.00 D
4) 2.00 D. 5) 5.00 D 6) 10.00 D. 7) 4.00 D. 8) 1.00 D 9) 8.00 D. 10) 20.00 D 11) 0.25 D. 12) 2.00 D. 13) 0.50 D 14) 5.00 D. 15) 1.00 D 16) 2.00 D. 17) 0.50 D. 18) 4.00 D 19) 20.00 D |
|
|
If we add a -2.00 lens to a +3.00 D lens, the combination will be ___ D lens.
|
+1.00 D
|
|
|
Which of the following is the stronger lens?
1) 20" FL or 40" FL 2) 50 cm FL or 20" FL lens 3) 1m FL lens or 100 cm FL or 80" FL lens |
1) 20" FL is stronger
2) They are the same 3) 1 m FL and 100 cm FL are the same |
|
|
The FL of a +2.00 lens is 20". If we add another +2.00 lens to it, the FL of this combination will be (shorter/longer) than 20".
|
The FL of a +2.00 lens is 20". If we add another +2.00 lens to it, the FL of this combination will be <shorter> than 20".
|
|
|
In a cylinder lens the light passes undeviated along its ___.
|
In a cylinder lens the light passes undeviated along its <axis>.
|
|
|
What is a cylinder lens?
|
Visualized as one cut from a cylinder. Meridian of no curvature while perpendicular to meridian power 90 degrees away from meridian.
|
|
|
What is a toric lens?
|
Also called spherocylinder lens that has two powers that are located 90 degrees from each other.
|
|
|
What is a sphere lens?
|
When a base curve with a single radius and diopter value combines with an occular curve with a single point of focus. Same power at all meridians.
|
|
|
Where are the focal points of plus and minus lenses?
|
Minus: focal point is in front of the lens.
Plus: focal point behind the lens Page 24 |
|
|
What type of lens is used to correct astigmatism?
|
Cylinder lenses/ toric
Page 30 |
|
|
Where in the image formed in a myopic eye? What lens corrects myopia?
|
The image is formed in front of the retina due to eye having too much power or the eye is too big. Minus lenses correct it.
Page 29 |
|
|
Where is the image formed in a hyperopic eye? What lens corrects hyperopia?
|
The image is formed behind the retina due to the eye not having enough power or small eyes. Plus lenses correct it.
Page 29 |
|
|
Which of these lenses has the shortest FL?
-7.00, +2.00, -5.00, +6.50 |
-7.00
|
