Prism definitions and characteristics.

1. Where is the thickest point on a prism that has no lens power?
   Where is the thinnest point on a prism that has no lens power?
2. Describe what a prism does to incident white light. Include both dispersion and deviation.
   

3. When viewed through a prism that is held base down, the image of an object will be

displaced up.
displaced down.
in the same position as the object.
4. Two rays of light that are parallel to each other before they enter a prism will exit

converging toward each other.

diverging from each other.
parallel to each other.

5. A particular beam with a purple hue is actually composed of some blue waves, some purple waves and some red waves. What will you see after this beam passes through the prism? What is the name of the principle involved?


6. When a prism is held with the base to the left, the image viewed through the prism will be

displaced to the right.
displaced to the left.
in the same position as the object.



Prism power definitions.


7. The angle that the sides of a prism form is called the


8. The factors that affect how much a ray will be deviated by a prism are


9. If a prism has an apical angle of 12 degrees and is made from a material with an index of refraction of 1.50, what will the angle of deviation be?


10. If a prism has an apical angle of 12 degrees and is made from a material with an index of refraction of 1.80, what will the angle of deviation be?


11. If a prism is to deviate light by 18 degrees and is to be made from a material with an index of refraction of 1.50, what apical angle should it have?


12. If a prism is to deviate light by 18 degrees and is to be made from a material with an index of refraction of 1.80, what apical angle should it have?


13. If a prism has an apical angle of 7 degrees and it displaces an incident ray of light by 4.5 degrees, what is the index of the material that the prism was made from?

(Round to two decimal places.)
14. For a very strong prism, which will be more accurate?

the prism diopter.
the centrad.
the prism diopter and the centrad are equal.
15. A 3.5 diopter prism will displace the image of an object that is 0.5 meters away from the prism by

cm
16. A prism is to displace an object that is 2 meters away by 45 cm. What power prism is necessary?


17. A 7.25 diopter prism displaces an image 14.5cm. How far away is the object that is being viewed?

m
18. What power will a prism made from a 1.66 material be if it has an apical angle of 13 degrees?

(Round to one decimal place.)



Prentice's rule.


19. If a pair of glasses with a plus prescription are made so that the wearer is looking above the optical center of the lens, that type of prism will the wearer experience?

base up.
base down.
base in.
base out.
20. A pair of minus lenses are cut so that the optical centers are farther apart than the wearer's pupils. What type of prism will the wearer experience?

base up.
base down.
base in.
base out.
21. When the glasses wearer looks down through the bottom of plus lenses, what type of prism will the wearer experience?

base up.
base down.
base in.
base out.
22. If the Doctor asks for BO prism and the glasses Rx has minus power, where should the optical center be with respect to the wearer's pupil?

up.
down.
in.
out.
23. Why?


24. How much prism is in effect 3 mm above the oc of a -2.50 DS lens?

base
25. If a ray travels through a +6.50 DS lens, entering it 4 mm to the right of the optical center, what will its angle of deviation be?

(First, find the prism.
Now use the formula for .) degrees. (Round to one decimal place.)