The Lens Equation
Part of the Optics, Waves and Modern Physics section of Coddy's Physics journey. Lesson 13 of 53.
The lens equation, distances from the lens:
1/u + 1/v = 1/f
Real is positive: u and v positive when real, f positive for a converging lens.
u = 30 cm, f = 20 cm: 1/v = 1/20 − 1/30, so v = 60 cm.
Object at 2F: image at 2F, same size. Object at F: no image, the light leaves parallel.
Challenge
An object stands 30 cm in front of a converging lens of focal length 20 cm. How far v behind the lens does its image form?
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Optics, Waves and Modern Physics
1Reflection and Refraction
Reflection of LightThe Refractive IndexSnell's LawTotal Internal ReflectionDispersionApparent DepthRecap - Optical Fiber4Mechanical Waves
What a Wave IsTwo Graphs of a WaveWhen Pulses MeetInterferenceStanding WavesHarmonicsRecap - Guitar String