1.  Using the equation,   explain in what situation would the image plane and the focal length be the same distance?  How could you use this to determine the focal length of an unmarked lens?
 
 

2.  Based on the fact that the Fourier Transform of a slit is mathematically identical to the far field diffraction pattern of light passing through a similar slit,  how would you expect the Fourier Transform of a triangle placed in the beam to appear in the focal plane?  What about a circle?  Draw your predictions.
 

3.  Using the wave properties of light, describe how refraction works. (Remember a picture is worth a thousand words and will add to your verbal description).