Which is the square number which is just after $49$ ?

A square number is obtained by multiplying a number by itself.

The first ten square numbers are

$1=1\times 1$

$4=2\times 2$

$9=3\times 3$

$16=4\times 4$

$25=5\times 5$

$36=6\times 6$

$49=7\times 7$

$64=8\times 8$

$81=9\times 9$

$100=10\times 10$

Therefore, the square number that is just after $49$ is $64$ i.e the correct answer is option B.