AQA · GCSE · Physics

    Course version: 8463 · Version from Sept 2016

    The image produced by a concave lens is always virtual.

    Full specification wording

    Lenses (physics only): The image produced by a concave lens is always virtual.

    A concave lens diverges the light: rays arriving parallel to the principal axis leave the lens spreading apart, as though they had come from a point on the same side as the object.

    Checked against the AQA 8463 specification (opens in a new tab) on .

    • Point 6 of 9
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    A concave lens diverges the light: rays arriving parallel to the principal axis leave the lens spreading apart, as though they had come from a point on the same side as the object. Because they spread rather than converge, they can never cross beyond the lens, so no real image is possible wherever the object is placed. Tracing the emerging rays backwards with dotted lines shows where they appear to come from, and that is the virtual image. For a concave lens it is always upright, always smaller than the object and always on the same side of the lens as the object, lying between the lens and its principal focus. It cannot be formed on a screen because no light actually arrives at that position.

    What earns the marks

    • The ray through the centre of the lens drawn without deviation.
    • The parallel ray drawn diverging as though it came from the principal focus on the same side.
    • The image located in the correct position using dotted construction lines.
    • The image drawn upright and smaller than the object.

    Common mistakes and how to put them right

    • Drawing the image from a concave lens inverted, by copying the convex lens case.

    • Placing the image beyond the lens on the far side from the object.

    • Using solid lines for the backward projections, which implies light really travels there.

    • Saying the image can be caught on a screen because it looks clear when viewed through the lens.

    Exam tips

    • For a concave lens the answer to what kind of image is always virtual, upright and diminished.
    • Use dotted lines for the projections and a solid arrow for the image itself.
    • Check that the image sits between the lens and F, because that is where the construction always places it.

    Try the lesson

    The start of the Lenses (physics only): The image produced by a concave lens is always virtual. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which type of image is always produced by a concave lens?

    Listen

    A concave lens diverges the light: rays arriving parallel to the principal axis leave the lens spreading apart, as though they had come from a point on the same side as the object. Because they spread rather than converge, they can never cross beyond the lens, so no real image is possible wherever the object is placed. Tracing the emerging rays backwards with dotted lines shows where they appear to come from, and that is the virtual image. For a concave lens it is always upright, always smaller than the object and always on the same side of the lens as the object, lying between the lens and its principal focus. It cannot be formed on a screen because no light actually arrives at that position. A strong answer earns marks for these points. the ray through the centre of the lens drawn without deviation. the parallel ray drawn diverging as though it came from the principal focus on the same side. the image located in the correct position using dotted construction lines. the image drawn upright and smaller than the object. Exam tip: For a concave lens the answer to what kind of image is always virtual, upright and diminished.

    See it

    A top-down flowchart. It starts with the object placed in front of a concave lens, then rays arriving parallel to the principal axis, then the concave lens diverging the light, then the emerging rays spreading apart. From the spreading rays the flow goes to rays traced backwards with dotted lines, then to a virtual image appearing on the same side as the object. That image node branches to two properties: the image is upright and smaller than the object, and the image lies between the lens and the principal focus. Separately, the spreading rays lead to the rays never crossing beyond the lens, and then to no real image, so it cannot be formed on a screen.
    It shows how a concave lens diverges parallel rays so that backward projections give a virtual, upright, diminished image on the same side as the object, which cannot be caught on a screen.

    Key words

    Say what each word means before you turn the card.

    diverging lens

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    always virtual

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    upright and diminished

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    dotted projections

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    See every definition
    diverging lens
    A concave lens spreads apart rays that arrive parallel to the principal axis, as though they had come from a point on the same side as the object.
    always virtual
    The image produced by a concave lens is always virtual, because the rays spread rather than converge and can never cross beyond the lens.
    upright and diminished
    For a concave lens the image is always upright and always smaller than the object.
    dotted projections
    Tracing the emerging rays backwards with dotted lines shows where they appear to come from, and that is the virtual image.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. It starts with the object placed in front of a concave lens, then rays arriving parallel to the principal axis, then the concave lens diverging the light, then the emerging rays spreading apart. From the spreading rays the flow goes to rays traced backwards with dotted lines, then to a virtual image appearing on the same side as the object. That image node branches to two properties: the image is upright and smaller than the object, and the image lies between the lens and the principal focus. Separately, the spreading rays lead to the rays never crossing beyond the lens, and then to no real image, so it cannot be formed on a screen.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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