5. (0.5 Points) Which wavelengths of light are most important for a good sunscre

Question

5. (0.5 Points) Which wavelengths of light are most important for a good sunscreen to block? A. Wavelengths very close to the one I calculated in the previous question B. Wavelengths greater than or equal to the one I calculated in the previous question. C. Wavelengths less than or equal to the one I calculated in the previous question. D. All wavelengths are equally important to block. E. The idea that sunscreen prevents sunburn is a myth created by multi-national corporations, so it does not matter what wavelengths are blocked. For problems 6-14, you will be investigating the Discharge Lamps Simulation: http://phet.colorado.edu/en/simulation/discharge-lamps (or go to the course website). Begin by exploring the 1-atom panel and the Configurable Atom. (A few non-obvious simulation controls: You can select the # of empty electronic energy levels in the configurable atom and adjust their location. And you can move the atom about in the discharge tube.) Consider the following True/False statements: 6. (0.5 Points) If the spacing between two electronic energy levels in atom A is smaller than in atom B, then the wavelength of the light emitted by atom B will be longer. (True/False) 7.(0.5 Points) If the spacing between two electronic energy levels in atom A is smaller than in atom B, then fewer photons will be emitted by atom B. (True/False) 8. (0.5 Points) Photons are emitted as electrons in the atom jump up in energy. (True/False)

Explanation / Answer

hi,

In the 5th question you dint specify the wavelength you calculated in the previous question. so, i m posting my answer in considering the general conditions of wavelength.

Our sunlight consists of many other rays besides useful vitamin-D. Those are harmful Ultravoilet(UV) rays. When these high energy photons strike your skin, they may damage skin cells, and even DNA depending on the wavelength.

So, applying sunscreen is like protecting your skin with a thin bullet proof. The UV range varies from over 290nm to 400nm wavelength. The shorter range is termed as UVB and longer as UVA.

Any sunscreen product has a Sun Protection Factor(SPF) value on it. This spf value gives the information of the number of photons it can block.

For eg: a sunscreen with SPF 20 can only allow 5 out of 100 photons striking the skin.

Its not a myth created by multi-national companies about sunscreens but they truely block the UV Rays out of skin.

---> The energies of emited wavelength is related with the transitions of energy levels as follows:

During energyhigh to energylow transition, the greater is the energy level difference, larger is the energy produced in the form of photons and shorter is the wavelength of the photons.

6. Since, the spacing between energy levels is more in atom B than A, the energy released in the form of Photons is more. Hence the wavelength is small.

So, the statement is false.

7. Since, the spacing is more in atom B than in atom A, the energy released will be more. Hence, the number of electrons released will also be more.

So, the statement is false.

8.Photons will be emitted when the electrons jump back to the lower energy levels not when they jump up in energy.

So, the statement is false.

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