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GCSE Physics · key term
An image formed where light rays only appear to come from; it cannot be projected onto a screen.
Used by AQA, Edexcel and OCR
Specification 4.6.2.5 · Paper 2
An image formed where light rays appear to come from when traced backwards; it cannot be projected onto a screen.
Revise: LensesExtend them backwards with dashed lines; where those extensions meet, on the object side, is the tip of an upright, magnified virtual image. At exactly the focal point, the emerging rays are parallel, so they do not form an image at a finite distance.
Specification 5.6P · Paper 1
An image formed where light rays appear to come from, found by extending the outgoing rays backwards. It cannot be projected onto a screen at that position.
Revise: Real and Virtual ImagesA virtual image forms when the outgoing rays do not actually meet, but appear to come from a common point. Extending the rays backwards with dashed lines locates this apparent origin.
Specification P5.3c · Paper 2 (Foundation), Paper 4 (Higher)
An image formed where light rays only appear to originate; it cannot be projected onto a screen.
Revise: Ray diagrams and lensesWhen these rays are extended backwards, they appear to come from an upright, enlarged virtual image on the object's side of the lens. This is how a magnifying glass is used.
Paper 1, Paper 2
Revise: Reflection, Refraction and LensesThe actual rays leaving a concave lens do not meet. Their backward extensions locate a virtual image on the same side of the lens as the object; for a real object this image is upright and diminished. The focus of a concave lens is therefore a point from which rays appear to diverge, whereas the far focus of a convex lens is a point at which parallel rays actually converge.
Use solid lines for actual light rays. Use dashed lines only when extending diverging rays backwards to locate a virtual image or focal point.
For a virtual image, draw the actual rays as solid lines and their backward extensions as dashed lines. Rays only appear to meet at the virtual image.
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