Sunday, August 16, 2015

Still Looking For Brewster

From the post "Late Bloomer Gets The Splits" dated 10 Aug 2015,

\(B_1sin(\alpha_{adj\,\,1})=B_2sin(\alpha_{adj\,\,2})\)

\(\cfrac{B_1}{\mu_1}cos(\alpha_{adj\,\,1})=\cfrac{B_2}{\mu_2}cos(\alpha_{adj\,\,2})\)

\(\alpha_{adj\,\,1}=90^o+\alpha_1-\theta_1\)

\(\alpha_{adj\,\,2}=90^o+\alpha_2-\theta_2\)

but when,

\(\alpha_1=\theta_1\)

\(cos(\alpha_{adj\,\,1})=cos(90^o)=0\)

or when,

\(\alpha_2=\theta_2\)

\(cos(\alpha_{adj\,\,2})=cos(90^o)=0\)

in which case,

\(\mu_1tan(\alpha _{adj\,\, 1 })=\mu_2tan(\alpha _{adj\,\, 2 })\)

is not valid,

The tangential component of the incident ray is zero and the ray enters the medium perpendicular to the inter-surface, parallel to the normal.  \(\alpha_{2s}\) passes through the second medium perpendicularly.

In a similar way, when we consider the left arm,

\(B_1sin(\alpha_{adj\,\,1})=B_2sin(\alpha_{adj\,\,2})\)

\(\cfrac{B_1}{\mu_1}cos(\alpha_{adj\,\,1})=\cfrac{B_2}{\mu_2}cos(\alpha_{adj\,\,2})\)

\(\alpha_{adj\,\,1}=\theta_1+\alpha_1-90^o\)

in the first medium, and into the second medium,

\(\alpha_{adj\,\,2}=\theta_2+\alpha_2-90^o\)

If \(\theta_1+\alpha_1=90^o\)

\(sin(\alpha_{adj\,\,1})=sin(0^o)=0\)

or when,

\(\theta_2+\alpha_2=90^o\)

\(sin(\alpha_{adj\,\,2})=sin(0^o)=0\)

the perpendicular component of the left incident arm is zero.  The tangential component  \(\alpha_{2p}\), glides along the surface (if it is flat) and does not enter the second medium.

Both scenario occurs when,

\(\theta_1=\alpha_1\)

and

\(\theta_2+\alpha_2=90^o\)

The incident ray is split \(90^o\) one along the surface \(\alpha_{2p}\), and the other enters the second medium perpendicularly \(\alpha_{2s}\).  This is wrong, velocity along the ray was not accounted for.


This is still not Brewster angle.  But, from

\(\theta_2+\alpha_2=90^o\)

\(\theta_2=90^o-\alpha_2\)

\(\theta_1=\alpha_1\)

Since, from the post "A Bloom Crosses Over" dated 10 Aug 2015,

\(\cfrac{ tan(\theta_1)}{tan(\theta_2)}=\cfrac{\varepsilon_2}{\varepsilon_1}\)

\(\cfrac{ tan(\alpha_1)}{tan(90^o-\alpha_2)}=\cfrac{\varepsilon_2}{\varepsilon_1}\)

\({ tan(\alpha_1)}{tan(\alpha_2)}=\cfrac{\varepsilon_2}{\varepsilon_1}\)

From Snell's Law,

\(n_1sin(\alpha_1)=n_2sin(\alpha_2)\)

\(\cfrac{n_1}{n_2}\cfrac{ sin^2(\alpha_1)}{cos(\alpha_1)cos(\alpha_2)}=\cfrac{\varepsilon_2}{\varepsilon_1}\)

and

\(\cfrac{ sin^2(\alpha_1)}{cos(\alpha_1)cos(\alpha_2)}=\cfrac{\varepsilon_2}{\varepsilon_1}\cfrac{n_2}{n_1}\)

\(\alpha_1+\alpha_2=90^o\)  This is wrong!

\(\cfrac{ sin^2(\alpha_1)}{cos(\alpha_1)cos(90^o-\alpha_1)}=\cfrac{\varepsilon_2}{\varepsilon_1}\cfrac{n_2}{n_1}\)

\(\cfrac{ sin(\alpha_1)}{cos(\alpha_1)}=tan(\alpha_1)=\cfrac{\varepsilon_2}{\varepsilon_1}\cfrac{n_2}{n_1}\)

which is still not Brewster.