Ultraviolet (uv) radiation is a part of the electromagnetic spectrum that reaches the earth from the sun. it has wavelengths shorter than those of visible light, making it invisible to the naked eye. these wavelengths are classified as uva, uvb, or uvc, with uva the longest of the three at 317 nm to 400 nm. both the u. s. department of health and human services and the world health organization have identified uv as a proven human carcinogen. many experts believe that, especially for fair-skinned people, uv radiation frequently plays a key role in melanoma, the deadliest form of skin cancer, which kills more than 8000 americans each year. uvb has a wavelength between 280 nm and 317 nm. determine the frequency ranges of uva and uvb. uva hz (smaller value) hz (larger value) uvb hz (smaller value) hz (larger value)

UVA:

UVB:

Explanation:

The formula to calculate the frequency of each electromagnetic wave is:

where

is the speed of light

is the wavelength

For UVA:

- The minimum wavelength is

so the frequency is

- The maximum wavelength is

so the frequency is

For UVB:

- The minimum wavelength is

so the frequency is

- The maximum wavelength is

so the frequency is

-first use of geothermal energy occurred more than 10,000 years ago in north america by american paleo-indians

-the first industrial use of geothermal energy began near pisa, italy in late 18th century

-in 1904, italian scientist piero ginori conti invented the first geothermal electric power plant in which steam was used to generate the power

-with the above experiment, the first geothermal plant in usa started in 1922 with a capacity of 250 kilowatts

-however, in 1946 first ground-source geothermal heat pump installed at commonwealth building in portland, oregon

-during the 1960’s, pacific gas and electric began operation of first large scale geothermal power plant in san francisco, producing 11 megawatts

-in 1973, when oil crisis began many countries began looking for renewable energy sources and by 1980’s geothermal heat pumps (ghp) started gaining popularity in order to reduce heating and cooling costs

-as effect of climate change started showing results, governments of various countries joined hands to fight against it, for which kyoto protocol was signed in japan in 1997, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it

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