Modern Physics

X-Rays

Since, the wavelength of X-Ray's is small they were not diffracted using the normal diffraction gradients. A crystal did diffract X-Ray's.

The distance (d) between the molecules makes the diffraction different for each path.

The reflection of the X-Ray's are different depending upon which path they are able to take.

Diffraction of X-Ray's from a crystal takes place at only certain incident angles that satisfy the following equation.

Bragg Equation:

(1)

 

Example 1

A beam of quasimonochromatic X-rays with a wavelength of 0.15 nm is incident on a crystal. What is the space between atomic planes if the first order diffraction maximum occurs at ?

 

Solution:

 

Atomic Spectra

 

Balmer series:

Lyman series:

Paschen series:

 

Example 2

For the hydrogen spectra above find the longest and shortest wavelengths in the Balmer series of spectral lines.

 

Solution:

For the longest substitute n = 3 into the series:

For the shortest n is infinite, therefore the second term goes to zero:

 

On to Photoelectric Effect