NBEO Part 1 Optics
Top 25 Beginner NBEO Part 1 Optics Questions (With Answers)
Optics is one of the most intimidating subjects for many optometry students. The good news is that most board questions are built on a relatively small number of fundamental principles. Once you understand these concepts, more advanced optics becomes much easier.
If you're just starting your NBEO Part 1 preparation, these 25 beginner questions will help you build a strong foundation.
1. What type of lens corrects myopia?
Answer: A minus (concave) lens.
Board Pearl: Minus lenses diverge light rays before they enter the eye, allowing the image to focus on the retina.
2. What type of lens corrects hyperopia?
Answer: A plus (convex) lens.
Plus lenses converge incoming light rays so the image moves forward onto the retina.
3. What unit measures lens power?
Answer: Diopters (D).
One diopter equals the reciprocal of the focal length in meters.
4. What is the formula for lens power?
Answer:
Power (D) = 1 ÷ Focal Length (meters)
Example:
A focal length of 0.50 m has a power of:
1 ÷ 0.50 = +2.00 D
5. A +4.00 D lens has what focal length?
Answer:
1 ÷ 4 = 0.25 meters (25 cm)
6. Which lens is thicker in the center?
Answer: A plus lens.
7. Which lens is thinner in the center?
Answer: A minus lens.
8. Which lens converges light?
Answer: A plus lens.
9. Which lens diverges light?
Answer: A minus lens.
10. What is emmetropia?
Answer: An eye with no refractive error.
Parallel light focuses directly on the retina without accommodation.
11. What is myopia?
Answer: Light focuses in front of the retina.
12. What is hyperopia?
Answer: Light focuses behind the retina when accommodation is relaxed.
13. What is astigmatism?
Answer: The eye has different powers in different meridians, producing two principal focal lines instead of a single point focus.
14. Which lens corrects astigmatism?
Answer: A cylindrical (toric) lens.
15. What does the optical center of a lens do?
Answer: Light passing through the optical center experiences minimal prismatic effect.
16. What happens when you look away from the optical center of a lens?
Answer: Prism is induced.
17. Which rule calculates induced prism?
Answer: Prentice's Rule
Prism = Decentration (cm) × Lens Power (D)
18. What does PD stand for?
Answer: Pupillary Distance
It is the distance between the centers of the pupils.
19. What is accommodation?
Answer: The eye's ability to increase optical power by changing the shape of the crystalline lens to focus on near objects.
20. What is presbyopia?
Answer: The age-related loss of accommodation caused by decreased flexibility of the crystalline lens and changes in the accommodative system.
21. What is vergence?
Answer: The amount of convergence or divergence of light.
It is measured in diopters.
22. What happens to light when it enters a denser medium?
Answer: It slows down and bends (refracts) according to Snell's Law.
23. What is refraction?
Answer: The bending of light as it passes between materials with different refractive indices.
24. What is total internal reflection?
Answer: Light is completely reflected back into a material when it strikes the boundary at an angle greater than the critical angle while traveling from a higher to a lower refractive index.
This principle is used in fiber optic cables and many ophthalmic instruments.
25. Which optics formula should every student memorize first?
Answer:
Power (D) = 1 ÷ Focal Length (meters)
This equation serves as the foundation for many additional optics calculations encountered on the NBEO.
Beginner Optics Formulas to Memorize
Start with these essential formulas:
Power (D) = 1 ÷ Focal Length (m)
Prism = cF (Prentice's Rule)
Magnification = Image Size ÷ Object Size
Vertex Power Formula (introduced later in your studies)
Mastering these will make advanced optics much easier.
Common Beginner Mistakes
Many students lose easy points because they confuse:
Plus lenses vs. minus lenses
Myopia vs. hyperopia
Converging vs. diverging lenses
Focal length vs. lens power
Optical center vs. prism
Accommodation vs. convergence
Take time to understand these relationships rather than memorizing isolated facts.
Final Study Tip
Optics can seem overwhelming at first, but every advanced topic builds on these basic principles. Focus on mastering the fundamentals before tackling more complex concepts like vergence calculations, thick lenses, vertex distance changes, and Gaussian optics.
Practice a few optics questions every day instead of saving them for the end of your study schedule. Short, consistent review sessions are one of the best ways to build confidence and improve retention.
At OD on the GO, our NBEO Part 1 review program includes comprehensive optics video lectures, interactive flashcards, worked calculation examples, and board-style practice questions designed to help students master optics from the basics through advanced problem solving.