I want to know what type of sentence the sentence below is and why we use two past participles in it.I took this sentence from a chemistry book; chemistry is my subject.

1) Concentration of CO2 and water vapour absorb infrared radiation emitted by earth surface.

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    Look up infrared in a dictionary: it's not a participle, infrare + -d but an adjective/color name, infra + red, like ultraviolet. Commented Jul 20, 2016 at 10:57
  • The sentence works in the same way as saying: ... radiation which is emitted by earth surface. It's a participle clause.
    – Schwale
    Commented Jul 20, 2016 at 20:21

1 Answer 1


In English there are many irregular verbs (Ex: 'to see' is an irregular verbs: the past is 'I saw' not 'I seed').

'Infrared' isn't a verb at all. 'Infrared' is 'infra' + 'red'.

'Emit' uses rules for regular verbs (verbs + ed) and we can divide 'emitted' into 'emit' (verb in present form) + 'ed'. Using this rule it should be 'emited', but in English when there is a consonant you have to double it and the full word becomes 'emitted'.

If you want look at some other forms of the verb to 'emit', you can look here

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