posted by Justin .
1. Find the lattice parameter of pure iron at room temperature.
2. What is the ratio of the lattice parameter of the iron to the wavelength of the radiation used.
3. What is the value of two theta for the second peak?
4. By what factor is the lattice parameter of the Fe bigger than the spacing of the second peak?
This must refer to some lab experiemnt of data obtasined from an experiment. I have no idea what radiation was used, and what you mean by the "second peak."
You also don't explain what "two theta" means in terms of the experiment.
The lattice paramenter can be obtained from the density and the crystal structure type (BCC), for iron.