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Infection and response
Organisation
Cell biology
Biological molecules
Homeostasis and response
Responding to change (a2 only)
Energy transfers (a2 only)
The control of gene expression (a-level only)
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
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1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
Britain & the wider world: 1745 -1901
Inter-war germany
World war one
2n revolution and dictatorship: russia, 1917-1953
World war two & the holocaust
1l the quest for political stability: germany, 1871-1991
The cold war
2j america: a nation divided, c1845-1877
Medieval period: 1066 -1509
The fight for female suffrage
2m wars and welfare: britain in transition, 1906-1957
2d religious conflict and the church in england, c1529-c1570
Britain: 1509 -1745
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03/04/2023
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EMISSION and ABSORPTION SPECTRA lighs and electromagnetic radiation: light is a form of electromagnetic radiation Electromagnetic radiation is energy travelling as waves A ware is described by its frequency (f) and its wavelength (& matre) f = £ The frequency and wavelength of light are related by the equation. C = FA (en the speed of light) 100x101-1 The frequency of electromagnetic radiation and energy (E) are connected by the equation. E= ht (A is Planck's comment) 6.63 A 10-343 Therefore, f & E. and is frequency increases, energy increases fx 1/² and if frequency increases, wavelength decreases. The whole range of frequencies of electromagnetic radiation is called the electromagnetic spectrum. Wavelength 104 104 104 104 101 101 10² 101 10 10⁰ 10 30 10 10⁰ Gamma ray Uravale Vald 400 Värava Blue STUDY POINTS 480 Infrared Visible spectam Green 640 580 Wareling in (am) Rada waves Aes Intramed It is important to note that both and energy frequency increase going from the infared through visible to the ultraviolet region. Thus, blue light is of a higher frequency than red light. As frequency gets larger and therefore wavelength decreases, blue light must have a shorter wavelength than red light. Light is electromagnetic radiation in the range. of wavelength corresponding to the visible region of the electromagnetic spectrum. Wavelength is the distance over which the wave's shape repeats. Frequency (n He) is the number of times the wave is repeated in one second. ABSORPTION SPECTRA light of all...
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visible wavelengths is called white light. All atoms and molecules absorb light of certain wavelengths. Therefore, when white light is passed through the rapour of an element, certain wavelengths will be absorbed by the atoms and removed through the light. Looking through a spectrometer, black lines appear in the spectrum where light of some wardengths has been absorbed. The wavelengths of these lines correspond to the energy taken in by the atoms to promote electrons from lower to higher energy levels. increasing wavelength. EMISSION SPECTRA when atoms are given energy by heating or by an electrical field, electrons are excited and the additional energy promotes them from a lover energy level to a higher one when the source of energy. is removed and the electrons leave the excited state, they fall from the higher energy level to a lower energy level and the energy lost is released as a Photon ( quantum of light overgy) with a specific frequency. The observed spectrum consists of a number of coloured lines on a black background nconig 1=40=2 4th 3rd 2nd 7:34912 118 transition-Balmer waretengre The fact that only certain colours appear in an atom's emission spectrum means that only photons having certain energies are emitted by the atom If the electron energy levels were not quantised but could have any value, a continuous spectrum rather than a line. spectrum would result. EMISSION SPECTRA Lowest energy lowest frequency Highest wardengen Red line λ = 656 nm to find energy E=hc λ E-6-63x10-34 x 3.00×108 656 x 10-9 E = 3·03x10-19 J Absorption Spectra: electrons. promoted I absorb energy and are to a higher energy level. ATOMIC ABSORPTION Electrons absorb energy - move to a higher energy level. ATOMIC EMISSION Excited elections fall to a lower energy. level and emit a photon Discrete lines. F=hf 4 = C/₂ E = n²/₂ - energy levels have fixed values transitions between correspond to same f. ↑ E= 14 ↑ f = la 4 E=LA ATOMIC EMISSION 475 450 400 300 100 SALMER SERIES (n=2) visible region LYMAN SERIES (n=1) UV region Atomic Emission: excited electron falls to a lower energy level and emits a photon.. CONVERGence limit n=1 to 11=00 2 = 92nm calculate 1 ie. E = no E = 2.16 × 10-15 J KJ mat E = 663x1024 x 3:00×108 92 x 104 Avogadro constant NA 6-02 x 1028 mol-1 PASCHEN SERIES (1:3) IR = 2.16 x 10-18 J x NA = 1301498 Jmo +1000=1301 KJ met n=∞ n=1 1:0 1=6 n=5 904 n=3 ・1=2