Objective: Determine the focal length of a lens using the Bessel method
On an optical bench it is possible to set up a light source, a lens, a screen and an object to be imaged in such a way that a well focussed image appears on the screen. Using the geometric relationships between the ray paths for a thin lens, it is possible to determine its focal length.
![Experiment: Lens Equation, 8000678 [UE4010100-230], Complete Experiments on Optics](/imagelibrary/UE4010100-230/UE4010100-230_01_Experiment-Lens-Equation.jpg)
![Experiment: Lens Equation, 8000678 [UE4010100-230], Complete Experiments on Optics](/thumblibrary/UE4010100-230/UE4010100-230_01_1200_1200_Experiment-Lens-Equation.jpg)
![Optical Bench K, 1000 mm, 1009696 [U8475240], Optical System Kroencke – Accessories](/thumblibrary/U8475240/U8475240_01_140_140_Optical-Bench-K-1000-mm.jpg)
![Optical Rider K, 1000862 [U8475350], Optical System Kroencke – Accessories](/thumblibrary/U8475350/U8475350_01_140_140_Optical-Rider-K.jpg)
![Clamp K, 1008518 [U84755401], Optical System Kroencke – Accessories](/thumblibrary/U84755401/U84755401_01_140_140_Clamp-K.jpg)
![Optical Lamp K, 1000863 [U8475400], Optical System Kroencke – Accessories](/thumblibrary/U8475400/U8475400_01_140_140_Optical-Lamp-K.jpg)
![Transformer 12 V, 25 VA (230 V, 50/60 Hz), 1000866 [U8475470-230], Power Supplies](/thumblibrary/U8475470-230/U8475470-230_01_140_140_Transformer-12-V-25-VA-230-V-5060-Hz.jpg)
![Converging Lens K, f = +50 mm, 1000869 [U8475901], Optical System Kroencke – Accessories](/thumblibrary/U8475901/U8475901_01_140_140_Converging-Lens-K-f-50-mm.jpg)
![Converging Lens K, f = +100 mm, 1010300 [U8475911], Optical System Kroencke – Accessories](/thumblibrary/U8475911/U8475911_01_140_140_Converging-Lens-K-f-100-mm.jpg)
![Projection Screen K, White, 1000879 [U8476320], Optical System Kroencke – Accessories](/thumblibrary/U8476320/U8476320_01_140_140_Projection-Screen-K-White.jpg)
![Set of 4 Image Objects, 1000886 [U8476605], Student Kits – Accessories](/thumblibrary/U8476605/U8476605_01_140_140_Set-of-4-Image-Objects.jpg)
![Precision Dynamometer 5 N, 1003106 [U20034], Dynamometers](/thumblibrary/U20034/U20034_01_140_140_Precision-Dynamometer-5-N.jpg)
![Tripod Stand 150 mm, 1002835 [U13270], Bases](/thumblibrary/U13270/U13270_01_140_140_Tripod-Stand-150-mm.jpg)
![DC Power Supply, 0-20 V, 0-5 A, 1003312 [U33020-230], Power Supplies](/thumblibrary/U33020-230/U33020-230_01_140_140_DC-Power-Supply-0-20-V-0-5-A.jpg)
![Clamp with Hook, 1002828 [U13252], Clamps](/thumblibrary/U13252/U13252_01_140_140_Clamp-with-Hook.jpg)
![Set of 15 Safety Experiment Leads, 75 cm, 2.5 mm², 1002843 [U138021], Circuits](/thumblibrary/U138021/U138021_01_140_140_Set-of-15-Safety-Experiment-Leads-75-cm-25-mm.jpg)
![Set of 10 Beakers,600 ml, Tall Form, 1002873 [U14211], Glassware](/thumblibrary/U14211/U14211_01_140_140_Set-of-10-Beakers-600-ml-Tall-Form.jpg)
![Stainless Steel Rod 750 mm, 1002935 [U15003], Stainless Steel Rod](/thumblibrary/U15003/U15003_01_140_140_Stainless-Steel-Rod-750-mm.jpg)
![Laboratory Jack II, 1002941 [U15020], Jacks](/thumblibrary/U15020/U15020_01_140_140_Laboratory-Jack-II.jpg)
![Immersion Block Al 100 cm³, 1002953 [U15037], Buoyancy](/thumblibrary/U15037/U15037_01_140_140_Immersion-Block-Al-100-cm.jpg)
![Set of Weights 1 g to 500 g, 1010189 [U29576], Balance Weights](/thumblibrary/U29576/U29576_01_140_140_Set-of-Weights-1-g-to-500-g.jpg)
![Experiment: Archimedes’ Principle, 8000526 [UE1020850], Buoyancy](/thumblibrary/UE1020850/UE1020850_01_140_140_Experiment-Archimedes-Principle.jpg)