Reflection at Curved Mirrors Study Guide: NEB 11 Physics

Learning boundary

What curved-mirror mastery requires

The CDC secondary curriculum requires object-image-focal relations, image-size relation, focal-length calculations and applications. Check the CDC Physics Grade 11 page for current Nepal material.

Use the paired curved-mirror concept guide for theory and OpenStax mirror image formation for an institutional comparison.

Three linked representations

Build words, diagram and equation together

If one representation disagrees, do not average the answers. Find whether the object region, ray rule, sign convention or arithmetic failed.

Seven sessions

A practical curved-mirror sequence

Use 55-minute blocks: ten minutes drawing from memory, ten minutes correction, thirty minutes mixed questions and five minutes error coding.

Construction discipline

Draw rays that carry evidence

1. Draw the principal axis, mirror, P, F and C to scale.
2. Place the object relative to F and C.
3. From the object tip draw a parallel ray and reflect through or away from F.
4. Draw a ray through or toward F and reflect parallel.
5. Use the C ray as a check.
6. Use dashed backward extensions only for a virtual image.

Arrowheads show propagation. Every construction must start from the same object point. Angles in the law of reflection are measured from the local normal, whose direction is toward C.

Retrieval table

Predict every image case

Cover two columns and reconstruct them from a diagram. Merely reciting the table is weaker than explaining why rays meet or appear to meet.

Quantitative routine

Keep sign convention visible

Write your convention before 1/f=1/u+1/v and m=h_i/h_o=−v/u, or use the exact convention taught by your school. Predict sign and region from the diagram first.

Practical evidence

Estimate focal length and uncertainty

Form a sharp image of a safe distant object on a screen with a concave mirror; pole-to-screen distance estimates f. Never use the Sun. Repeat, measure from the pole and report spread. A finite object distance makes the estimate slightly different from the infinite-object ideal.

For a u–v investigation, take several object positions outside F, focus the image and record distances. Check 1/f against 1/u+1/v or plot a transformed graph. Screen-position judgement, pole reference, alignment and spherical aberration affect results.

Use PhET Geometric Optics after predicting rays, and confirm the simulation’s mirror mode.

Spaced correction

Code the first wrong decision

Use geometry, ray rule, extension, image language, sign convention, formula, scale or uncertainty. Redo after one, three and seven days. Link to Physical Quantities for unit discipline and Vectors Study Guide for direction conventions.

Final test

Readiness checklist and transfer tasks

• P, F, C and ray directions are labelled.
• Virtual extensions are dashed.
• Image nature is predicted before equations.
• One sign convention is used consistently.
• Magnification sign and magnitude are interpreted.
• f=R/2 is linked to paraxial approximation.
• Experimental uncertainty is explained.

1. Draw all concave cases.
2. Draw one convex case.
3. Solve three formula questions.
4. Find R from distant focus.
5. Evaluate a u–v method.

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References and next steps

Sources and related study guides

• CDC Nepal: Physics Grade 11
• CDC Nepal: Secondary Curriculum
• OpenStax: Law of Reflection
• OpenStax: Mirror Image Formation
• OpenStax: Optics Questions
• PhET: Geometric Optics

Continue with Refraction at Plane Surfaces. Curriculum scope and sources were checked on 2 August 2026; follow current CDC, NEB and college instructions if requirements change.

Transfer challenge

Move one object through every region

Draw one concave mirror and slide an object through five labelled positions. For each, predict where the image moves, how orientation changes and whether a screen can receive it. Then calculate one case from each side of F. This continuous story is harder to forget than six isolated table rows.

Explain the discontinuity at F carefully: the ideal image distance grows without bound as the object approaches F from outside; inside F the image is virtual behind the mirror. The physical rays change continuously even though the image description crosses infinity.

Sign and scale workbook

Make the convention testable

Create a page with three columns: predicted region, signed data and calculated result. For a concave real-image case, the image should lie in front of the mirror and the magnification should indicate inversion. For an object inside F, the image should lie behind the mirror and magnification should indicate upright enlargement. A convex real-object case should remain virtual, upright and diminished.

Use one school-approved sign convention throughout the page. Write the positive direction, signs of f, u and v, and the meaning of height signs. If a source uses a different convention, translate the definitions before comparing formulas; never copy only the signs.

Finish with an application comparison: a concave examination mirror places the object inside F to give an upright enlarged view, while a convex road or shop mirror accepts a diminished image to gain a wider field. State the trade-off rather than calling either mirror universally “better.”

Application audit

Choose a mirror from image requirements

A close examination mirror needs an upright enlarged virtual image, so the object must be inside a concave focus. A vehicle or shop mirror prioritises a wide field and upright virtual image, so convex curvature is useful despite diminished detail. A searchlight places a compact source near a concave focus to send approximately parallel rays.

For each application, write the desired image nature first, then select mirror and object region. Mention paraxial approximation, aperture and alignment as limitations. This turns a memorised list into an optical design argument.