Blue and red lasers (with wavelengths 475 nm and 633 nm, respectively) are shone through a diffraction grating towards a wall 4.2 m away. Each laser produces a pattern of dots on the wall and the dots from both patterns are very close together in three locations, each separated by 3.1 m.

The ratio of lift to drag l/d for a wing or airfoil is an important aerodynamic parameter, indeed, it is a direct measure of the aerodynamic efficiency of the wing. if a wing is pitched through a range of angle of attack, l/d first increases, then goes through a maximum, and then decreases. consider an infinite wing with an naca 2412 airfoil. estimate the maximum value of l/d. assume that the reynolds number is 9x10^6.