IB Environmental systems and societies Topic 6.4A UV Radiation Revision Notes (SL/HL)

IB Environmental systems and societies Topic 6.4A UV Radiation Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Solar Radiation: Why Wavelength Decides Biological Impact

Definition

Electromagnetic radiation

Electromagnetic radiation is energy that travels as oscillating waves through space and includes radio waves, infrared, visible light, ultraviolet, X-rays and gamma rays.

The Sun emits electromagnetic (EM) radiation across a continuous spectrum, from low-frequency radio waves to high-frequency gamma rays.
Shorter wavelengths carry more energy, so they have the greatest potential to harm living tissue.
Only part of this radiation reaches the surface, because the atmosphere absorbs and reflects the rest.
Three bands matter for life: infrared, visible light and ultraviolet.
1. Infrared radiation warms the surface and atmosphere, keeping global temperatures suitable for life.
2. Visible light drives photosynthesis, setting the productivity of land and aquatic ecosystems.
3. Ultraviolet (UV) radiation is high-energy and can damage living cells.

Radiation Type	Wavelength Range	Major Source
Infrared (IR)	~700 nm – 1 mm	Sun, Earth’s emitted energy
Visible Light	400 – 700 nm	Sun
Ultraviolet (UV)	100 – 400 nm	Sun

Analogy

Visible light is the fuel that powers ecosystems.
UV radiation is an overcharge of energy that can burn or destroy biological tissue.

UVA, UVB and UVC: Three Bands of Rising Danger

UV has shorter wavelengths and higher frequencies than visible or infrared light, so it carries more energy.
The higher the frequency, the greater the potential to damage DNA, cells and tissues.
UV is divided into three biologically important types, which the ozone layer filters very differently.

Type	Wavelength	Harm Level	Ozone Absorption	Key Effects
UVA	315–400 nm	Least harmful	Mostly reaches the surface	Skin ageing, contributes to cancer
UVB	280–315 nm	Highly harmful	Mostly absorbed, some reaches the surface	DNA mutation, skin cancer, sunburn
UVC	100–280 nm	Extremely harmful	Completely absorbed by ozone	Would be lethal if it reached the surface

Common Mistake

Many students assume UVA is harmless because it only causes tanning.
UVA still contributes to skin cancer.
It also causes immune suppression and premature ageing.

The Ozone Layer: Earth’s UV Shield

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Definition

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Note

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Tip

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Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
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Solar Radiation: Why Wavelength Decides Biological Impact

Definition

Electromagnetic radiation

Electromagnetic radiation is energy that travels as oscillating waves through space and includes radio waves, infrared, visible light, ultraviolet, X-rays and gamma rays.

The Sun emits electromagnetic (EM) radiation across a continuous spectrum, from low-frequency radio waves to high-frequency gamma rays.
Shorter wavelengths carry more energy, so they have the greatest potential to harm living tissue.
Only part of this radiation reaches the surface, because the atmosphere absorbs and reflects the rest.
Three bands matter for life: infrared, visible light and ultraviolet.
1. Infrared radiation warms the surface and atmosphere, keeping global temperatures suitable for life.
2. Visible light drives photosynthesis, setting the productivity of land and aquatic ecosystems.
3. Ultraviolet (UV) radiation is high-energy and can damage living cells.

Radiation Type	Wavelength Range	Major Source
Infrared (IR)	~700 nm – 1 mm	Sun, Earth’s emitted energy
Visible Light	400 – 700 nm	Sun
Ultraviolet (UV)	100 – 400 nm	Sun

Analogy

Visible light is the fuel that powers ecosystems.
UV radiation is an overcharge of energy that can burn or destroy biological tissue.

UVA, UVB and UVC: Three Bands of Rising Danger

UV has shorter wavelengths and higher frequencies than visible or infrared light, so it carries more energy.
The higher the frequency, the greater the potential to damage DNA, cells and tissues.
UV is divided into three biologically important types, which the ozone layer filters very differently.

Type	Wavelength	Harm Level	Ozone Absorption	Key Effects
UVA	315–400 nm	Least harmful	Mostly reaches the surface	Skin ageing, contributes to cancer
UVB	280–315 nm	Highly harmful	Mostly absorbed, some reaches the surface	DNA mutation, skin cancer, sunburn
UVC	100–280 nm	Extremely harmful	Completely absorbed by ozone	Would be lethal if it reached the surface

Common Mistake

Many students assume UVA is harmless because it only causes tanning.
UVA still contributes to skin cancer.
It also causes immune suppression and premature ageing.

The Ozone Layer: Earth’s UV Shield

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

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Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

IB Environmental systems and societies 6.4A UV Radiation Notes

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

Solar Radiation: Why Wavelength Decides Biological Impact

UVA, UVB and UVC: Three Bands of Rising Danger

The Ozone Layer: Earth’s UV Shield

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Solar Radiation: Why Wavelength Decides Biological Impact

UVA, UVB and UVC: Three Bands of Rising Danger

The Ozone Layer: Earth’s UV Shield

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account