course phy202 With the thicker convex lens, when the light is 50cm from the screen, the screen must be moved to 6.8cm to make the sharpest image (h<1mm). When the light is 40cm from the screen, the screen must be moved to 7.1cm to make the sharpest image (h=1mm). When the light is 30cm from the screen, the screen must be moved to 7.5cm to make the sharpest image (h=1.25mm). When the light is 20cm from the screen, the screen must be moved to 8.6cm to make the sharpest image (h=2mm).