AP Physics Questions: Myopia, Hyperopia, and Lens Power

📚 Quick Study Guide

• 👓 Myopia (Nearsightedness): Image focuses *in front* of the retina. Corrected with diverging (negative) lenses.
• 👁️ Hyperopia (Farsightedness): Image focuses *behind* the retina. Corrected with converging (positive) lenses.
• 📏 Lens Power (P): Measured in diopters (D). $P = \frac{1}{f}$, where $f$ is the focal length in meters.
• ➕ Converging Lens: Positive focal length, positive power. Bends light rays inward.
• ➖ Diverging Lens: Negative focal length, negative power. Bends light rays outward.
• 📐 Corrective Lens Formula: To correct vision, the lens power needed $P = \frac{1}{d_o} + \frac{1}{d_i}$, where $d_o$ is the object distance (usually infinity for far vision) and $d_i$ is the desired image distance (distance to the far point).
• 🧐 Far Point: The farthest distance at which an object can be seen clearly without corrective lenses.

🧪 Practice Quiz

1. Which of the following describes myopia?
   1. Image focuses behind the retina.
   2. Image focuses on the retina.
   3. Image focuses in front of the retina.
   4. Image focuses at the optic nerve.
2. What type of lens is used to correct hyperopia?
   1. Diverging lens
   2. Converging lens
   3. Cylindrical lens
   4. Prismatic lens
3. A person has a far point of 50 cm. What lens power is needed to correct their vision?
   1. +2.0 D
   2. -2.0 D
   3. +0.5 D
   4. -0.5 D
4. What is the unit of lens power?
   1. Meter
   2. Diopter
   3. Watt
   4. Hertz
5. A lens has a focal length of 0.25 meters. What is its power?
   1. 2 D
   2. -2 D
   3. 4 D
   4. -4 D
6. Which of the following is true for a diverging lens?
   1. It has a positive focal length.
   2. It has a negative power.
   3. It converges light rays.
   4. It is used to correct myopia.
7. A person requires a -1.5 D lens. What vision problem do they likely have?
   1. Hyperopia
   2. Presbyopia
   3. Myopia
   4. Astigmatism