Excel i need to lookup names between two sheets

hi hope you guys can help i have brain freeze at the mo

i have a list of accounts number that i need to lookup names

so on sheet 1 i have
a
74921101
74922331
74922331
74922461
74922461
74927161
74927161
74927171
74927171
844533551

and on sheet 2 i have
a                        b
74921101        company a
74922331        company b
74922461        company c
74927171        company d
844533551      company e

what I want is on sheet 1 cell b to show sheet 2 b name

a                          b
74921101        company a
74922331        company b
74922331        company b
74922461        company c
74922461        company c

Hope this all makes sense

James