[Tex/LaTex] Permanent Transparent Block in a Frame in Beamer

Question

In a frame I have two blocks: the first is visible, while the second should be transparent.

With

\frame{
\frametitle{title}
\begin{block}{title visible block}
\end{block}
\invisible{\begin{block}{title invisible block}
\end{block}}
}

The first block is visible and the second one invisible. I would like to make the second block transparent rather than invisible.
How can I do this?

EDIT:

This is partially the code of 3 slides.

\frame{
\frametitle{title}
\begin{block}<1->{procedure-1}
 \begin{center}
   \includegraphics[height=1.3in,width=4in]{images/procedure-1.png}
 \end{center}
\end{block}
\invisible{\begin{block}{Mathematical Formulation}
\begin{equation}
 0+0=0
\end{equation}
\end{block}}
}
\frame{
\frametitle{title}
\begin{block}<1->{procedure-2}
 \begin{center}
   \includegraphics[height=1.3in,width=4in]{images/procedure-2.png}
 \end{center}
\end{block}
\invisible{\begin{block}{Mathematical Formulation}
\begin{equation}
 0+0=0
\end{equation}
\end{block}}
}
\frame{
\frametitle{title}
\begin{block}<1->{procedure-3}
 \begin{center}
   \includegraphics[height=1.3in,width=4in]{images/procedure-3.png}
 \end{center}
\end{block}
\begin{block}<2->{Mathematical Formulation}
\begin{equation}
 0+0=0
\end{equation}
\end{block}
}

Answer 1

Quoting the manual:

\invisible<⟨overlay specification⟩>{⟨text⟩}

This command is the opposite of \visible.

So, what does \visible do? Quoting again the manual:

\visible<⟨overlay specification⟩>{⟨text⟩}

This command does almost the same as \uncover. The only difference is that if the text is not shown, it is never shown in a transparent way, but rather it is not shown at all. Thus, for this command the transparency settings have no effect.

Therefore, if you really want to have the second block transparent, you don't have to use \invisible.

You can use \onslide for example, of course by specifying first \setbeamercovered{transparent}:

\documentclass{beamer}
\usepackage{lmodern}
\usepackage{mwe}% for dummy images
\usepackage{amsmath}
\usetheme{CambridgeUS}
\setbeamercovered{transparent}
\begin{document}
\begin{frame}
\only<1>{
\begin{block}{procedure-1}
 \centering% use this and not the center environment
 \includegraphics<1>[height=1.3in,width=4in]{example-image}
\end{block}
}
\only<2>{
\begin{block}{procedure-2}
 \centering% use this and not the center environment
 \includegraphics<2>[height=1.3in,width=4in]{example-image-a}
\end{block}
}
\only<3->{
\begin{block}{procedure-3}
 \centering% use this and not the center environment
 \includegraphics<3->[height=1.3in,width=4in]{example-image-c}
\end{block}
}
\onslide<4>{
\begin{block}{Mathematical Formulation}
\begin{equation}
 0+0=0
\end{equation}
\end{block}
}
\end{frame}
\end{document}

The result: