CAIE IGCSE Physics 3.2.3.6 Ray Diagrams for the Formation of a Questions

Construct virtual images by tracing emerging rays backwards, read image positions from scaled lens diagrams, and use a supplied image to locate its object.

Exam points

Draw two valid rays from the same object point, extend the emerging rays backwards, and label the upright virtual image at their intersection.
Measure the virtual-image distance from the lens centre along the principal axis, converting the diagram measurement with its stated scale.
Work backwards from a supplied virtual image and focal points to locate the object, placing its tip at the construction-line intersection.
Explain why a constructed image is virtual: the emerging rays do not meet there, their backward extensions do, and the image cannot be projected on a screen.
Select the object position between a converging lens and its principal focus when a diagram must produce a virtual image.

[Maximum number: 4]

Fig. 6.1 shows a thin converging lens used to produce a magnified image of an object AB.

Fig. 6.1

On Fig. 6.1, draw the magnified image of AB. Show your working.

any two from:

- ray from top of object to lens, parallel to principal axis, refracted to $F_{2}$

- ray from top of object through centre of lens, undeviated

- ray from $F_{1}$ , through top of object and on to lens, then parallel to principal axis
rays extrapolated back to converge to the left of $\mathrm{F}_{1}$
image drawn from principal axis to intersection with arrow (to show orientation)

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CAIE IGCSE Physics 3.2.3.6 Ray Diagrams for the Formation of a Questions question 1