Physics, 20.03.2020 03:02 yalley1982

After applying sunscreen, Cherie lies in the summer sun to get a tan. The ultraviolet light responsible for tanning has a wavelength over 310. nm, while the burning rays can range down to 280. nm. Which ultraviolet photons emit more energy, those that tan or those that burn?

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Answer from: nelly1078

The photons that burn, emit more energy.

Explanation:

The energy of the ultraviolet photons can be determined by means of the following equation:

$E = h\nu$ (1)

Equation 1 can be rewritten in terms of $\lamba$

Since, $c = \nu \lambda$

$\nu = \frac{c}{\lambda}$

$E = \frac{hc}{\lambda}$ (2)

Where h is the planck's constant, c is the speed of light and $\lambda$ is the wavelength.

Case for the photon of with $\lambda = 310nm$

$\lambda = 310nm . \frac{1x10^{-9}m}{1nm}$ ⇒ $3.1x10^{-7}m$

$E = \frac{hc}{\lambda}$

$E = \frac{(6.626x10^{-34}J.s)(3x10^{8}m/s)}{3.1x10^{-7}m}$

$E = 6.412x10^{-19}J$

Case for the photon of with $\lambda = 280nm$

$\lambda = 280nm . \frac{1x10^{-9}m}{1nm}$ ⇒ $2.8x10^{-7}m$

$E = \frac{hc}{\lambda}$

$E = \frac{(6.626x10^{-34}J.s)(3x10^{8}m/s)}{2.8x10^{-7}m}$

$E = 7.099x10^{-19}J$

Hence, the photons that burn, emit more energy.

Answer from: Quest

-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

hope this

Answer from: Quest

we need to know the time interval during which the force acts. impulse of force = momentum change

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After applying sunscreen, Cherie lies in the summer sun to get a tan. The ultraviolet light responsi...

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