Đáp án:
A
Giải thích các bước giải:
$\begin{align}
& {{n}_{1}}=1,4;{{i}_{1}}=1,2mm \\
& {{n}_{2}}=1,6mm \\
\end{align}$
vận tốc truyền sóng:
$\dfrac{{{v}_{1}}}{{{v}_{2}}}=\dfrac{{{n}_{2}}}{{{n}_{1}}}=\dfrac{1,6}{1,4}=\dfrac{8}{7}$
bước sóng:
$\begin{align}
& f=\dfrac{{{v}_{1}}}{{{\lambda }_{1}}}=\dfrac{{{v}_{2}}}{{{\lambda }_{2}}} \\
& \Rightarrow \dfrac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\dfrac{{{v}_{1}}}{{{v}_{2}}}=\dfrac{{{n}_{2}}}{{{n}_{1}}}=\frac{8}{7} \\
\end{align}$
Khoảng vân:
$\begin{align}
& i=\dfrac{D.\lambda }{2}\Rightarrow \dfrac{{{i}_{1}}}{{{i}_{2}}}=\dfrac{{{\lambda }_{1}}}{{{\lambda }_{2}}}=\frac{8}{7} \\
& \Rightarrow {{i}_{2}}=1,2.\dfrac{7}{8}=1,05mm \\
\end{align}$