Science, Class 10: Light
Power of a Lens
P = 1/f · Unit: dioptre (D) · Convex +, concave -
By the end of the lesson you can
🔍Relate a lens's thickness to how much it bends light
📖Define the power of a lens
🧮Calculate power with P = 1/f, f in metres
➕Give the right sign for convex and concave lenses
Thin lens or thick lens?
🔹Thin convex lens
Small curvature
Bends rays gently
Focus far away: long f
Low power
VS
🔷Thick convex lens
Large curvature
Bends rays sharply
Focus close: short f
High power
Presenter notes: Today we find out why some lenses bend light more than others, and how one number, the power, tells us that.