Suppose you were stranded on a desert island with only a convex lens and a mirror. Describe how you could use each of these tools to signal for help. (
To signal for help with the convex lens, one could start a fire by focusing the sunlight through the lens onto some dry tinder or kindling. By moving the lens to track the sun's movement across the sky, one could maintain the fire and create a thick column of smoke that would be visible from a distance.
With the mirror, one could reflect the sunlight towards passing boats or planes by angling the mirror to catch the sunlight and then flashing the light towards the potential rescuer. By continuously flashing the mirror in a pattern (such as SOS), one could attract attention and signal for help effectively.