Chapter Name: Refraction Of Light At Curved Surfaces
Activity Name: Lens in cylindrical vessel in Refraction Of Light At Curved Surfaces
This experiment aims to investigate the refraction of light through a lens placed in a cylindrical vessel filled with water. By observing the image formation, the focal length of the lens in different media will be determined, highlighting the dependence of focal length on the surrounding medium.
- Convex lens (from Activity 2)
- Cylindrical glass vessel (e.g., glass tumbler) with a height much greater than the focal length of the lens
- Black stone
- Circular lens holder
Step by Step Procedure:
- Note down the average focal length of the convex lens obtained from Activity 2.
- Place the black stone at the bottom of the cylindrical vessel.
- Fill the vessel with water up to a height greater than the focal length of the lens.
- Horizontally dip the lens into the water using the circular lens holder, positioning it above the stone.
- Adjust the distance between the stone and lens to be equal to or less than the focal length of the lens measured in Activity 2.
- Observe the stone through the lens in an open ground.
- When the lens is dipped into the water and the distance between the stone and lens is less than the focal length of the lens, an image of the stone is visible.
- As the lens is raised further, the image of the stone becomes invisible.
- Handle the lens and glass vessel carefully to avoid any damage.
- Ensure the cylindrical vessel is filled with water to an appropriate height to obtain clear observations.
- Keep the surroundings well-lit for better image formation.
Lesson Learnt from Experiment:
The experiment demonstrates that the focal length of the lens changes when it is placed in a different medium. The focal length increases when the lens is in water compared to its focal length in air. This highlights the dependence of the lens’ focal length on the surrounding medium’s refractive index.