13. Five parallel rays of light are incident onto a concave reflective surface. They are reflected and pass through a focal point 8.4 cm away along the principal axis. What is the radius of curvature for the concave surface

When you see distant streetlights through smog, they look dimmer and redder than they do normally. but when you see the same streetlights through fog or falling snow, they look dimmer but not redder. use your knowledge of the interstellar medium to discuss the relative sizes of the particles in smog, fog, and snowstorms compared to the wavelength of light.