AQA · GCSE · Chemistry

    Course version: 8462 · Version from Sept 2018

    Students should be able to describe the greenhouse effect in terms of the…

    Full specification wording

    Greenhouse gases: Students should be able to describe the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter.

    The greenhouse effect depends on how radiation of different wavelengths interacts with matter.

    Checked against the AQA 8462 specification (opens in a new tab) on .

    • Point 2 of 2
    • 3 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    The greenhouse effect depends on how radiation of different wavelengths interacts with matter. Short wavelength radiation from the Sun, mainly visible and ultraviolet, passes through the atmosphere and is absorbed by Earth's surface, warming it. The warmed surface emits longer wavelength infrared radiation. Greenhouse gas molecules in the atmosphere absorb this infrared radiation because their bonds can vibrate at frequencies matching that energy. The absorbed energy is re-emitted in all directions, including back to Earth, so less escapes to space and the surface stays warmer. This is a continuous energy balance: incoming short wavelength radiation, outgoing long wavelength radiation, and absorption and re-emission by greenhouse gases.

    What earns the marks

    • Short wavelength radiation from the Sun, including visible and ultraviolet, passes through the atmosphere and is absorbed by Earth's surface.
    • Earth's warmed surface emits longer wavelength infrared radiation.
    • Greenhouse gas molecules absorb infrared radiation and re-emit it in all directions, including back towards Earth.
    • Because some infrared energy is returned, less energy escapes to space and surface temperature is maintained.
    • The interaction depends on wavelength: short wavelength radiation is largely transmitted, while long wavelength infrared is absorbed by greenhouse gases.
    • The process is a balance between incoming solar energy and outgoing infrared energy.

    Common mistakes and how to put them right

    • Saying greenhouse gases reflect infrared radiation.

      Put it right: They absorb and re-emit it, which is different from reflection.

    • Claiming short wavelength radiation is trapped by greenhouse gases.

      Put it right: It is mainly the longer wavelength infrared emitted by Earth that is absorbed.

    • Describing the greenhouse effect as a one-way trapping process.

      Put it right: Energy is continuously absorbed, re-emitted and partly lost to space.

    Exam tips

    • Use the terms 'short wavelength' for incoming solar radiation and 'long wavelength' or 'infrared' for radiation emitted by Earth.
    • Explain the sequence: Sun emits short wavelength, Earth absorbs and warms, Earth emits infrared, greenhouse gases absorb and re-emit.
    • Avoid saying heat is 'trapped' without explaining absorption and re-emission, as this shows the mechanism more clearly.

    Try the lesson

    The start of the Greenhouse gases: Students should be able to describe the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter. lesson, made from checked teaching notes for this specification point.

    Have a go first

    In the greenhouse effect, which type of radiation from the Sun passes through the atmosphere to reach the Earth's surface?

    Listen

    The greenhouse effect depends on how radiation of different wavelengths interacts with matter. Short wavelength radiation from the Sun, mainly visible and ultraviolet, passes through the atmosphere and is absorbed by Earth's surface, warming it. The warmed surface emits longer wavelength infrared radiation. Greenhouse gas molecules in the atmosphere absorb this infrared radiation because their bonds can vibrate at frequencies matching that energy. The absorbed energy is re-emitted in all directions, including back to Earth, so less escapes to space and the surface stays warmer. This is a continuous energy balance: incoming short wavelength radiation, outgoing long wavelength radiation, and absorption and re-emission by greenhouse gases. A strong answer earns marks for these points. Short wavelength radiation from the Sun, including visible and ultraviolet, passes through the atmosphere and is absorbed by Earth's surface. Earth's warmed surface emits longer wavelength infrared radiation. Greenhouse gas molecules absorb infrared radiation and re-emit it in all directions, including back towards Earth. Because some infrared energy is returned, less energy escapes to space and surface temperature is maintained. Exam tip: Use the terms 'short wavelength' for incoming solar radiation and 'long wavelength' or 'infrared' for radiation emitted by Earth.

    See it

    A top-down flowchart with nine boxes linked by arrows. The first box says the Sun emits short wavelength radiation, leading to a box saying short wavelength radiation passes through the atmosphere, then to a box saying Earth's surface absorbs radiation and warms. From there an arrow leads to a box saying the warmed surface emits longer wavelength infrared radiation, then to a box saying greenhouse gas molecules absorb infrared radiation, then to a box saying energy is re-emitted in all directions. This box branches into two: one box says some infrared returns to Earth, the other says less energy escapes to space. Both of these lead into a final box saying the surface stays warmer.
    It shows the sequence of the greenhouse effect, from incoming short wavelength radiation to absorption and re-emission of infrared radiation by greenhouse gases and the resulting warmer surface.

    Key words

    Say what each word means before you turn the card.

    Absorption and re-emission of radiation

    Try answering aloud or in your head before turning the card.

    Earth's energy balance

    Try answering aloud or in your head before turning the card.

    Greenhouse effect mechanism

    Try answering aloud or in your head before turning the card.

    See every definition
    Absorption and re-emission of radiation
    Greenhouse gas molecules absorb infrared radiation because their bonds can vibrate at frequencies matching that energy, and the absorbed energy is re-emitted in all directions, including back to Earth.
    Earth's energy balance
    A continuous balance between incoming short wavelength radiation, outgoing long wavelength radiation, and absorption and re-emission by greenhouse gases.
    Greenhouse effect mechanism
    Short wavelength radiation from the Sun passes through the atmosphere and is absorbed by Earth's surface, which then emits longer wavelength infrared radiation that greenhouse gases absorb and re-emit.

    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 with nine boxes linked by arrows. The first box says the Sun emits short wavelength radiation, leading to a box saying short wavelength radiation passes through the atmosphere, then to a box saying Earth's surface absorbs radiation and warms. From there an arrow leads to a box saying the warmed surface emits longer wavelength infrared radiation, then to a box saying greenhouse gas molecules absorb infrared radiation, then to a box saying energy is re-emitted in all directions. This box branches into two: one box says some infrared returns to Earth, the other says less energy escapes to space. Both of these lead into a final box saying the surface stays warmer.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

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