i would like to know important issue.

we are knowing that the address field of instruction is virtual address.
well, if so, how we can estimate the size of RAM by this field?

ex. if the address field =10 bits
now we can say , there are 2^10 location in RAM.

well, if 10 bits are width of virtual not physical address , how by which calculate the number of locations?
it is supposed the size of RAM be less than 2^10.
please, resolve this dilemma

thanks in advance