🔭 Individual Worksheet
Physics – Grade 8 | Lenses. Power of lenses. The formula of thin lens
👤 Student: _____________________________ 📅 Date: _____________ 🎯 Goal: 8.5.1.11 – Use thin lens formula in problems
📘 Instructions for the student:- Read each task carefully. Write your answers in the provided spaces.
- Show all steps, formulas, and calculations where required.
- Use 1f = 1d₀ + 1dᵢ and P = 1f (in metres).
- You may work independently; you can ask for hints after trying each problem.
- Total marks for this worksheet: 10 points.
📌 Task 1 – Lens formula basics 2 points
1.1 Write down the thin lens formula. What does each symbol represent?
1.2 A converging lens has a focal length of 15 cm. An object is placed 30 cm from the lens. Using the formula, calculate the image distance dᵢ. Show all steps.
📌 Task 2 – Optical power 2 points
2.1 Define optical power of a lens. Write the formula and give the unit.
2.2 A lens has a focal length of 25 cm. Calculate its optical power in diopters (D). (Hint: convert cm to metres first.)
📌 Task 3 – Find the unknown 2 points
An object is placed 12 cm from a thin lens. The image is formed on a screen 24 cm on the other side of the lens.
3.1 Calculate the focal length of the lens.