Optical Instruments: JAMB Physics Questions, Answers & Notes

What Optical Instruments covers in the JAMB Physics syllabus

Lenses are converging (convex) or diverging (concave). Lens power P = 1/f (f in metres, unit dioptre), and the lens formula is 1/f = 1/u + 1/v. A camera forms a real, inverted, diminished image; a magnifying glass (simple microscope) gives a virtual, upright, magnified image; a compound microscope uses two convex lenses for high magnification; telescopes view distant objects. In the eye, the cornea and lens focus a real, inverted image on the retina, the iris controls light, and accommodation adjusts the lens. Short sight is corrected with a concave lens, long sight with a convex lens.

For Optical Instruments, JAMB expects you to be able to:

• Distinguish converging (convex) and diverging (concave) lenses and lens power
• Apply the lens formula and describe images in cameras, microscopes and telescopes
• Describe the human eye, accommodation and correction of eye defects

Key facts & revision notes: Optical Instruments

These are the recurring points our Optical Instruments questions test — revise them until each feels automatic, then practise the questions above to lock them in.

• A convex lens converges parallel light to a focus, so it is a converging lens.
• A concave lens spreads out (diverges) parallel light, so it is a diverging lens.
• The retina is the light-sensitive screen at the back of the eye where images form.
• The iris adjusts the size of the pupil to control the light entering the eye.
• Myopia (can't see far) is corrected with a concave (diverging) lens.
• Hypermetropia (can't see near) is corrected with a convex (converging) lens.
• A simple microscope is a single convex lens used to give a magnified, upright, virtual image.
• A compound microscope has two convex lenses — an objective and an eyepiece — for high magnification.
• Power P = 1/f, where f is the focal length in metres; the unit is the dioptre (D).
• P = 1/f = 1/0.5 = 2 dioptres.
• The lens formula is 1/f = 1/u + 1/v.
• 1/10 = 1/30 + 1/v → 1/v = 1/10 − 1/30 = 3/30 − 1/30 = 2/30 → v = 15 cm.
• A camera's convex lens forms a real, inverted, diminished image on the film or sensor.
• Magnifying power indicates how much larger the image appears compared with the object.
• An astronomical telescope views distant objects such as stars and planets.
• The cornea does most of the refraction; the lens makes fine focusing adjustments.
• Accommodation is the eye lens changing shape (curvature) to focus objects at different distances.
• Used within its focal length, a convex lens (magnifying glass) gives a virtual, upright, magnified image.
• The eye lens forms a real, inverted image on the retina; the brain interprets it as upright.
• Since power = 1/f, a shorter focal length gives a higher power.
• Converging lenses bulge in the middle.
• Concave lenses spread parallel rays apart.
• P = 1/f = 1/0.25 = 4 dioptres.
• u is the object distance.

Worked examples

Three Optical Instruments questions with the answer and a short explanation, so you can see how the topic is set before you practise the full set.

How Optical Instruments is tested in JAMB Physics

Our Optical Instruments bank holds 40 questions (6 easy, 28 medium, 6 hard). JAMB Physics typically returns to Optical Instruments year after year, so steady practice on this topic is high-value revision. Questions are multiple-choice with four options, and at UTME pace you get roughly 40 seconds each — which is why timed practice matters.

How to answer Optical Instruments questions

Work the stem first and predict the answer before you look at the options; then eliminate the ones that contradict the key facts above. Watch for “which is not…”, “all of the above” and “except” style stems, which are where rushed candidates lose easy marks on Optical Instruments. If a calculation or a precise definition is involved, work it from first principles rather than guessing from a half-remembered rule. When two options look right, re-read the stem for the qualifier that separates them — JAMB rarely repeats an option by accident. If you are still unsure, eliminate the two weakest choices to lift your odds, flag the question, and move on; never burn a full minute on one Physics item when the exam gives you about forty seconds each. Then come back to flagged questions with whatever time remains. The single most reliable way to get faster at Optical Instruments is repeated timed practice, so use the button above until the recurring patterns feel automatic.

Common mistakes to avoid in Optical Instruments

The errors that cost marks on Optical Instruments are usually careless rather than conceptual: misreading a negative stem, confusing two similar terms, or rushing a definition you actually know. Candidates also over-rely on “expo” and last-minute cramming instead of understanding the topic — which fails the moment JAMB rephrases a familiar idea. Treat every option as a claim to be checked against the facts above, keep your working tidy for any calculation, and don’t change a considered answer on a hunch. Above all, revise Optical Instruments actively by answering questions, not just by re-reading notes — recall under time is what the exam rewards.

Frequently asked questions

Is Optical Instruments part of the JAMB Physics syllabus?

Yes. Optical Instruments is a recognised topic in the JAMB Physics syllabus, covering distinguish converging (convex) and diverging (concave) lenses and lens power. You should be able to recall its key facts and apply them to multiple-choice questions.

How many Optical Instruments questions can I practise on Belmadeng?

There are 40 original, JAMB-standard Optical Instruments questions in our free bank, each with the correct answer and a worked explanation. You can practise them untimed or as a timed test.

What are the most important points to know about Optical Instruments?

Lenses are converging (convex) or diverging (concave). Lens power P = 1/f (f in metres, unit dioptre), and the lens formula is 1/f = 1/u + 1/v. A camera forms a real, inverted, diminished image; a magnifying glass (simple microscope) gives a virtual, upright, magnified image; a compound microscope u…

How do I answer Optical Instruments questions quickly in JAMB?

Read the stem carefully, eliminate clearly wrong options, and match the remaining choices to the key facts for Optical Instruments. Practising timed Optical Instruments questions builds the speed you need for UTME's pace of about 40 seconds per question.

Are these JAMB Physics Optical Instruments questions past questions or original?

They are original questions written to JAMB (UTME) standard and mapped to the official syllabus — not reproduced past papers. This keeps them legal to use freely while closely mirroring how the real exam tests the topic.

Where can I practise Optical Instruments questions free without signing up?

Right here — tap “Start Optical Instruments practice” on this page to begin instantly. Belmadeng's CBT practice is completely free and needs no sign-up, download or subscription.

About these questions: original, JAMB-standard items written from the official UTME Physics syllabus (last reviewed 2026-09-18). Belmadeng is an independent study platform and is not affiliated with JAMB. Spotted an error? Use the report link.