<p>The value is $\beta \simeq -1$ (e.g. see  <a href="http://adsabs.harvard.edu/abs/1988ApJ...329L..33C" rel="nofollow noreferrer">Cardelli et al. 1988</a>). The extinction would not be well fitted by a power law, except over a very narrow wavelength range.</p>

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2018-09-19T07:43:14.223Z
2018-09-19T07:43:14.223Z
ProfRob
<p>I am curious to know If dust extinction were to vary as a power-law so that $A_{\lambda}$ proportionate to $\lambda^{\beta}$ , what value of beta
would give rise to Rv =3.1 which is the average in diffuse ISM. I can see a plot but I wanted to see how to derive Rv=3.1 mathematically</p>

<extinction>
Quesions about extinction power law
bhjghjh
# Quesions about extinction power law

(Asked by: username_0 on 2018-09-19)

I am curious to know If dust extinction were to vary as a power-law so that $A\_{\lambda}$ proportionate to $\lambda^{\beta}$ , what value of beta
would give rise to Rv =3.1 which is the average in diffuse ISM. I can see a plot but I wanted to see how to derive Rv=3.1 mathematically

**Tags:** extinction

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## 1 answers

### Answer by username_1 on 2018-09-19. Score: 1 | Accepted answer

The value is $\beta \simeq -1$ (e.g. see [Cardelli et al. 1988](http://adsabs.harvard.edu/abs/1988ApJ...329L..33C)). The extinction would not be well fitted by a power law, except over a very narrow wavelength range.


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