Question

Which among the following is a scalar matrix?

• A. $\left[\begin{array}{cc}1& 0\\ 0& 1\end{array}\right]$
• B. $\left[\begin{array}{cc}0& 2\\ 2& 0\end{array}\right]$
• C. $\left[\begin{array}{cc}5& 5\\ 5& 5\end{array}\right]$
• D. $\left[\begin{array}{cc}0& 0\\ 1& 1\end{array}\right]$

Answer 1

The correct option is A

$\left[\begin{array}{cc}1& 0\\ 0& 1\end{array}\right]$

Scalar matrix is essentially an identity matrix multiplied by a scalar constant. So in a way identity matrix itself will be a subset of scalar matrices where the concerned scalar will be equal to 1. Here none of the other matrices represent such a case. So the option will be (a).