Cells taken from a fungus are examined with a light microscope. Before eosin is applied, the structures cannot be distinguished clearly.
Why does adding eosin help?
it keeps the cells alive while they are being viewed
it makes the specimen thin enough for light to pass through
it gives different structures different depths of colour
it removes the air bubbles trapped under the cover slip
130 exam-style questions on OCR GCSE Biology 1.1 Cell structures, covering 1.1.1 Viewing cells with light microscopes, 1.1.2 Sub-cellular structures and functions, and 1.1.3 Electron microscopy and resolution. Each one has a worked solution and a mark scheme showing where the marks go.