UVA vs UVB: Why does UVA penetrate deeper into the skin?

In summary, UVA and UVB are both types of ultraviolet radiation from the sun, but UVA has longer wavelengths and is able to penetrate deeper into the skin. This is because UVA is not absorbed by the ozone layer, allowing it to reach the Earth's surface in higher amounts. UVA also has the ability to pass through glass and clouds, making it present even on cloudy days. While UVB is responsible for sunburns and skin damage, UVA is linked to more serious long-term effects such as premature aging and skin cancer. It is important to protect against both UVA and UVB rays for overall skin health.
  • #1
finnch
4
0
Hello,

My name is Chris and I am trying to understand why UVA radiation, with a longer wavelength, penetrates deeper into the skin than UVB which has a shorter wavelength.

Since E=hv=hc/ λ and
c44eb3c2af933606f2bb928132d7ec21.png
,

then how does a lower energy and lower intensity UVA wave penetrate deeper into the skin than a UVB wave?

Pardoning the pun, I would appreciate it if someone could enlighten me :eek:)

Many thanks...
 
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  • #2
In general, longer wavelength light will always pennetrate deeper into a scattering medium. This is the same reason why the sun appears red at sunset.
 
  • #3
Ygggdrasil said:
In general, longer wavelength light will always pennetrate deeper into a scattering medium. This is the same reason why the sun appears red at sunset.

Dear Sir,

Thank you for your reply but I disagree with your response. In our atmosphere, blue light, with a higher frequency (shorter wavelength) scatters more than red light with a longer wavelength and lower frequency. Scattering is proportional to frequency raised to the power of four...See

An X-Ray has a very high frequency, i.e short wavelength and penetrates both skin and bone and is consistent with the energy and intensity formulas cited earlier. So again, I am trying to find justification for why a longer wave, lower frequency UVA ray penetrates deeper than a shorter wave, higher frequency, higher energy, higher intensity UVB ray.

Thank you,

Chris
 
  • #4
finnch said:
Dear Sir,

Thank you for your reply but I disagree with your response. In our atmosphere, blue light, with a higher frequency (shorter wavelength) scatters more than red light with a longer wavelength and lower frequency. Scattering is proportional to frequency raised to the power of four...See

An X-Ray has a very high frequency, i.e short wavelength and penetrates both skin and bone and is consistent with the energy and intensity formulas cited earlier. So again, I am trying to find justification for why a longer wave, lower frequency UVA ray penetrates deeper than a shorter wave, higher frequency, higher energy, higher intensity UVB ray.

Thank you,

Chris
Sorry Ygggdrasil,

After a little more reflection, your response does make sense and the youtube video I posted earlier actually supports your response. I was looking for an explanation considering only the energy side of the question without considering the scattering when the light actually interacts with matter. So I guess that when dermatologists tell us that UVB burns more but UVA penetrates more deeply, then it's the scattering of the UVB along the surface of our bodies that causes the surface burn while the longer UVA transmits deeper into the skin without burning the surface as much?

Thank you for your help.

Chris
 

Related to UVA vs UVB: Why does UVA penetrate deeper into the skin?

1. What is the difference between UVA and UVB?

UVA and UVB are both types of ultraviolet radiation from the sun. UVA has a longer wavelength and can penetrate deeper into the skin, while UVB has a shorter wavelength and primarily affects the surface layers of the skin.

2. Why does UVA penetrate deeper into the skin?

UVA has a longer wavelength, which allows it to penetrate deeper into the skin compared to UVB. This is because longer wavelengths are able to pass through the outer layers of the skin more easily.

3. Is UVA or UVB more harmful?

Both UVA and UVB can be harmful to the skin, but in different ways. UVA has been linked to skin aging and wrinkles, while UVB is primarily responsible for sunburns and skin cancer. It is important to protect against both types of UV radiation.

4. Can UVA and UVB both cause skin cancer?

Yes, both UVA and UVB can contribute to the development of skin cancer. However, UVB is considered to be more damaging and is the primary cause of non-melanoma skin cancers, while UVA may play a smaller role in the development of melanoma.

5. How can I protect my skin from UVA and UVB?

The best way to protect your skin from both UVA and UVB is to use a broad-spectrum sunscreen with an SPF of 30 or higher. It is also important to seek shade, wear protective clothing, and limit sun exposure during peak hours (10am-4pm).

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