MHB What fraction of light do these glasses transmit

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Welders utilize a logarithmic scale to determine the shade number of protective eyewear based on the fraction of light transmitted, expressed in the equation n = 1 − (7logT)/3. For a welder using glasses that transmit ⅛ of the light, the calculation yields a shade number of approximately 6.5. Viewing a solar eclipse through #14 welding glasses is deemed safe, and the corresponding fraction of light transmitted can be calculated using the rearranged equation, resulting in T being approximately 0.0002. The discussion emphasizes the importance of understanding the logarithmic relationship in selecting appropriate protective eyewear. Accurate calculations are crucial for ensuring safety in welding and during solar events.
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Welders use a logarithmic scale to identify protective eyewear. The shade number n, is given by the
equation n = 1 − 7logT/3 , where T is the fraction of visible light that glass transmits.

a. What shade number should a welder use that only transmits ⅛ of the light entering the glass?
b Viewing a solar eclipse through #14 welding glasses is considered safe. What fraction of light do
these glasses transmit.
 
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fxacx said:
Welders use a logarithmic scale to identify protective eyewear. The shade number n, is given by the
equation n = 1 − 7logT/3 , where T is the fraction of visible light that glass transmits.

a. What shade number should a welder use that only transmits ⅛ of the light entering the glass?
b Viewing a solar eclipse through #14 welding glasses is considered safe. What fraction of light do
these glasses transmit.

is the equation $n=1-7\log \left(\dfrac{T}{3}\right)$ ... ?

please confirm
 

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fxacx said:
Welders use a logarithmic scale to identify protective eyewear. The shade number n, is given by the
equation n = 1 − (7log(T))/3 , where T is the fraction of visible light that glass transmits.

a. What shade number should a welder use that only transmits ⅛ of the light entering the glass?
So T= 1/8. n= 1- (7 log(1/8))/3. Can you do the arithmetic?

b. Viewing a solar eclipse through #14 welding glasses is considered safe. What fraction of light do these glasses transmit.
Now n= 14 so 14= 1- (7 log(T))/3. 14- 1= 13= -(7/3) log(T).
-(3/7)(13)= -39/7= log(T). Do you know how to "reverse" log?
 
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