ABO MIDTERM EXAMINATION STUDY
GUIDE QUESTIONS AND ANSWERS
100% VERIFIED. JUST RELEASED
1. Transpose the following prescription into minus cylinder form: -2.00 +1.50 x 090.
A. -3.50 +1.50 x 180
B. -2.00 -1.50 x 180
C. -0.50 -1.50 x 090
D. -0.50 -1.50 x 180
Answer: D
Conceptual Explanation: To transpose, add the sphere and cylinder (-2.00 + 1.50 = -0.50),
change the sign of the cylinder (-1.50), and rotate the axis by 90 degrees (090 to 180).
2. What is the refractive index of Polycarbonate?
A. 1.586
B. 1.530
C. 1.498
D. 1.660
Answer: A
,Conceptual Explanation: Polycarbonate has a refractive index of 1.586, which is higher
than CR-39 (1.498) and Trivex (1.530).
3. Using Prentice’s Rule, calculate the prism induced if a +4.00 D lens is decentered 5mm.
A. 0.2 prism diopters
B. 0.8 prism diopters
C. 20 prism diopters
D. 2.0 prism diopters
Answer: D
Conceptual Explanation: Prentice’s Rule is P = c * F, where c is centimeters of
decentration. 5mm = 0.5cm. 0.5 * 4.00 = 2.0 prism diopters.
4. Which material has the highest Abbe value, indicating the least chromatic aberration?
A. Polycarbonate
B. CR-39
C. Crown Glass
D. 1.67 High Index
Answer: C
Conceptual Explanation: Crown Glass typically has an Abbe value of around 58-59, the
highest among these options, meaning it has the lowest chromatic aberration.
, 5. When light travels from a medium of lower refractive index to a medium of higher
refractive index, the light rays:
A. Bend away from the normal
B. Travel in a straight line
C. Bend toward the normal
D. Reflect back completely
Answer: C
Conceptual Explanation: According to Snell’s Law, light entering a denser medium (higher
index) slows down and bends toward the normal line.
6. What is the focal length of a 2.00 D lens?
A. 2 meters
B. 20 cm
C. 100 cm
D. 50 cm
Answer: D
Conceptual Explanation: Focal length (f) = 1 / Diopters (D). .00 = 0.5 meters, which is
50 cm.
7. A lens clock is typically calibrated for a refractive index of:
A. 1.498
GUIDE QUESTIONS AND ANSWERS
100% VERIFIED. JUST RELEASED
1. Transpose the following prescription into minus cylinder form: -2.00 +1.50 x 090.
A. -3.50 +1.50 x 180
B. -2.00 -1.50 x 180
C. -0.50 -1.50 x 090
D. -0.50 -1.50 x 180
Answer: D
Conceptual Explanation: To transpose, add the sphere and cylinder (-2.00 + 1.50 = -0.50),
change the sign of the cylinder (-1.50), and rotate the axis by 90 degrees (090 to 180).
2. What is the refractive index of Polycarbonate?
A. 1.586
B. 1.530
C. 1.498
D. 1.660
Answer: A
,Conceptual Explanation: Polycarbonate has a refractive index of 1.586, which is higher
than CR-39 (1.498) and Trivex (1.530).
3. Using Prentice’s Rule, calculate the prism induced if a +4.00 D lens is decentered 5mm.
A. 0.2 prism diopters
B. 0.8 prism diopters
C. 20 prism diopters
D. 2.0 prism diopters
Answer: D
Conceptual Explanation: Prentice’s Rule is P = c * F, where c is centimeters of
decentration. 5mm = 0.5cm. 0.5 * 4.00 = 2.0 prism diopters.
4. Which material has the highest Abbe value, indicating the least chromatic aberration?
A. Polycarbonate
B. CR-39
C. Crown Glass
D. 1.67 High Index
Answer: C
Conceptual Explanation: Crown Glass typically has an Abbe value of around 58-59, the
highest among these options, meaning it has the lowest chromatic aberration.
, 5. When light travels from a medium of lower refractive index to a medium of higher
refractive index, the light rays:
A. Bend away from the normal
B. Travel in a straight line
C. Bend toward the normal
D. Reflect back completely
Answer: C
Conceptual Explanation: According to Snell’s Law, light entering a denser medium (higher
index) slows down and bends toward the normal line.
6. What is the focal length of a 2.00 D lens?
A. 2 meters
B. 20 cm
C. 100 cm
D. 50 cm
Answer: D
Conceptual Explanation: Focal length (f) = 1 / Diopters (D). .00 = 0.5 meters, which is
50 cm.
7. A lens clock is typically calibrated for a refractive index of:
A. 1.498
