Optics Challenge #1 — Thin Lens Equation

An image in a
converging lens.

Optics Medium

Problem

An object is placed 15 cm from a converging lens with a focal length of 10 cm. Use the thin lens equation to find the image distance from the lens.

Focal length\( f = 10\ \mathrm{cm} \)
Object distance\( u = 15\ \mathrm{cm} \)
Lens equation\( \tfrac{1}{f} = \tfrac{1}{u} + \tfrac{1}{v} \)
Answer incentimetres

Use the real-is-positive convention; the object is outside the focal length.

Hint: rearrange the lens equation so \( \tfrac{1}{v} \) stands alone: \( \tfrac{1}{v} = \tfrac{1}{f} - \tfrac{1}{u} \). Put both fractions over a common denominator before flipping.

Create a free account to solve

Submit your answer and unlock the full mark scheme.

Full mark schemes, not just answers
Earn XP and climb the leaderboard
Track your mastery, topic by topic

Create free account

Already have an account?

Finish a lesson to solve

Complete the Optics lessons to unlock solving and earn XP from this challenge — or skip ahead with Physi+.

Continue Learning

Or unlock everything with Physi+

You solved this challenge

You can open the mark scheme below. Check again anytime — no extra XP.

Submit your answer

Solve it on paper first — then check yourself.

Your answer

Numeric answers allow ±1% tolerance for rounding.

Up next · Nuclear Physics Half-Life of a Sample Keep the streak going — a fresh problem in Nuclear Physics.

Mark schemeClick to open

An image in aconverging lens.

Problem