There is one problem in the problem set i don't know how to approach it..(adsbygoogle = window.adsbygoogle || []).push({});

Problem:

While an artificial diffraction grating is used to study a spectrum of a light beam, electromagnetic waves with wavelengths much less than the wavelength of the visible light are used to study the natural diffraction

grid, namely a crystalline structure. Electromagnetic waves in this range are called the x-rays. The condition for constructive interference is given by Bragg’s law:

2dsin- = m+, m = 1, 2, 3, …

If the wavelength and diffraction angle are measured, the Bragg equation can be used to calculate the spacing between atomic planes.

In our problem, the crystalline of NaCl with density D = 2.16 g/cm3 is exposed to x-rays with the glancing angle - = 60.0o. The reflected rays form the second order maximum.

(a) Find the wavelength of x-rays used in the experiment.

(b) Explain why the visible light cannot be used to obtain the diffraction pattern on crystals.

i don't understand what equation relates the interplanar spacing and density together, or am i on the wrong track?

Thanks alot!

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Crystalline diffraction problem

Can you offer guidance or do you also need help?

**Physics Forums | Science Articles, Homework Help, Discussion**