I'm trying to make a makefile that supports c++11

It's a simple thing but I'm having trouble making a makefile.

It needs to support c++11 and I should be able to call it with ./radixsort in the linux terminal.

It just has two files, main.cpp and header.h

How would I write this up? So far every attempt doesn't work.

my last attempt:

radixsort: main.cpp header.h
     g++ -std=c++11 radixsort main.cpp header.h