The document discusses the principles of diffraction gratings and how they can be used to calculate various properties of light. Specifically, it explains the diffraction grating equation, provides examples of how to use it to determine the wavelength of light and angle of diffraction for different grating spacings and orders. It also describes how a grating's line spacing can be used to calculate the slit spacing and discusses the angular spread of a spectrum produced from a grating.

1. Diffraction http:// www.youtube.com/watch?v =a_qRKjeam5w

3. Spectra The burning salt on the knife in the candle shows up orange on the line spectra

4. Diffraction Grating Equation d sin θ = n λ d = distance between the slits Θ = angle to maxima n = integer number to next bright fringe λ = wavelength of light Number of slits per metre N = 1/d Sin θ can never be greater than 1, so there is a limit to the number of spectra that can be obtained.

5. d sin θ = n λ Red light will be seen at d = 1600nm λ = 600nm n = 1 sin θ = (1)*600nm/1600nm = 0.375 θ = sin -1 (0.375) = 22° If you used a DVD then θ would be 47.6°

7. Grating answers d sin θ = n λ 3.

8. Grating answers 4.

9. Diffraction through a single slit The middle fringe is twice the width of all the other fringes. The outer fringes are less intense than the first fringe (W) Width of the central fringe W =( λ a ) x D λ = wavelength a = width of single slit D= distance to the screen

10. The distance between the fringes (w) w