Optics & Waves · GCSE Physics Topic 6 (Waves & Optics)
Convex & Concave Lens Optical Bench Simulator
Key exam takeaway: 1f divides real vs virtual images; 2f divides enlarged vs diminished images. Covering half the lens still forms a complete image with halved brightness.
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- Live Derivation
- Projector Mode
- Print Worksheet
3D Simulation Stage● 60 FPS
Parameter Controls
cm
cm
cm
Live Derivations & Metrics
Image Distance v
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Magnification M
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Image Characteristics
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Practical Device
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Real-Time Formula Derivation
Governing Formula:
--Substitution:
--Regime: --
Worked Examples & Exam Question Deep Dive
Worked Problem
Problem: A convex lens with f=10cm has a candle at u=15cm. What are the image characteristics and image distance v?
Step-by-Step Derivation:
- 1/f = 1/u + 1/v => 1/10 = 1/15 + 1/v => v = 30cm. Since f < u < 2f, image is inverted, magnified and real.
Worked Problem
Problem: To observe an upright magnified virtual image using a convex lens of f=10cm, what range must object distance u satisfy?
Step-by-Step Derivation:
- Upright virtual images require object inside focal length (u < f). Distance must be between 0 and 10cm.
Student Inquiry Worksheet & Practice Problems
Q1. Variant 1: As candle burns shorter, which way does the image shift on the screen? How to re-center it?
Answer Key: Candle flame lowers, so its inverted image on screen moves upward. Lower lens and screen or raise candle.
Q2. Variant 2: Why might an image fail to appear on the screen despite moving it along the bench? (List 3)
Answer Key: 1) Candle inside f (virtual image); 2) candle at focal point (parallel rays); 3) flame, lens, and screen centers not aligned at equal height.
Q3. Variant 3: How do parallel rays refract through a concave lens? Which vision defect does it correct?
Answer Key: Parallel rays diverge with extensions meeting at virtual focus. Concave lenses correct myopia (nearsightedness).
Frequently Asked Questions & Misconceptions
Will covering the bottom half of a lens show only half an image?
No! Every zone of the lens converges rays to form the complete image. Occluding half reduces light throughput by half, making image dimmer.
How to distinguish nearsighted vs farsighted glasses by eye?
Nearsighted glasses are concave lenses (thinner center, thicker edges, diminishes views); reading glasses are convex lenses (thicker center, magnifies).
When moving closer for a photograph, should the lens extend forward or retract backward?
Closer object (smaller u) produces further image (larger v). The lens must extend forward away from the sensor to keep focus.
If object distance u = 2f, what is image distance and magnification?
Image distance v = 2f and magnification M = 1 (inverted equal-size real image). It serves as the benchmark to measure unknown focal length.