For example [1], 
1
0
0
1





 , 
1
0
0
0
1
0
0
0
1










 are identity matrices of order 1, 2 and 3,
respectively Observe that a scalar matrix is an identity matrix when k = 1 But every identity
matrix is clearly a scalar matrix Rationalised 2023-24
MATRICES         41
(vii)
Zero matrix
A matrix is said to be zero matrix or null matrix if all its elements are zero