Sir,This comment is very useful.I need to ask one thing.
If we have different block size in L1 and L2.Say
L1= 1 word block size with Access Time=2ns and L2=4 word block size with access time as 4 ns.
Now when there is a miss in L1,we will goto L2 and search one entire block to look for one particular word as asked by L1 and then if it is found,it will be transferred to the L1 cache. So basically we accessed one complete L2 block with 4*2=8ns but just to transfer it to L1,it is 1 word time as L1 block size is 1 word and i.e what is asked in the question