Diffraction gratings are hand held gratings in which there are thousands of tiny slits, designed to help determine the wavelength of the light passing through it. Wavelength or the angle can be found using the equation Wavelength=d*sin theta, where theta is the angle between the light traveling to the central bright band and the second order line, and d is equal to the distance between slits. These are used to separate light into it's component frequencies (i.e. white light turns into the spectrum). The spacing of the lines in a diffraction grating can be calculated by determining the lines per cm and dividing 1 by that number. The more lines in a grating, the sharper the image it gives, and diffraction errors can be improved upon by adding more lines per cm.