A student investigates how the concentration of a salt solution inside a hollow, double-convex lens affects its focal length.
The focal length fff of the lens is given by the equation:
f=uvu+v f = \frac{uv}{u+v} f=u+vuvwhere uuu is the distance between the illuminated object and the lens, and vvv is the distance between the lens and the sharp image formed on a screen.
Plan an experiment to investigate how the concentration of a salt solution affects the focal length of the hollow lens.
The following apparatus is available to the student:
Other laboratory apparatus normally available in a school laboratory can also be used.
In your plan, you should:
216 exam-style questions on CIE IGCSE Physics 3.2 Light, covering 3.2.1a Reflection of light, 3.2.1b Images in a plane mirror, 3.2.2 Refraction of light, 3.2.2a Refraction of light, 3.2.2b Total internal reflection, 3.2.2c Refractive index and critical angle, 3.2.2d Optical fibres, 3.2.3a Converging and diverging lenses, 3.2.3b Ray diagrams and the nature of images, 3.2.3c Virtual images and the magnifying glass, 3.2.3d Correcting long-sightedness and short-sightedness, and 3.2.4 Dispersion of light. Each one has a worked solution and a mark scheme showing where the marks go.