Format: Chart with lines of letters, starting with a large single letter at the top
Letter Type: Sans-serif, standardized optotypes (not standard alphabet fonts)
Distance: To be used at a standard distance of 6 meters (20 feet)
Visual Acuity Markings: Each line marked with corresponding Snellen fraction (e.g., 6/6, 6/9, 6/12, 6/18, 6/24, 6/36, 6/60, etc.)
Top Letter Size: Large enough to be seen by a person with 6/60 vision at 6 meters
Bottom Line Size: Small enough to correspond to 6/6 normal vision at 6 meters
Material: High-quality, non-reflective board or laminated plastic, or digitally printed on matte surface
Language: Usually in English letters, also be available in regional scripts or E-charts for non-literate patients
Dimensions: around 22 x 56 cm (vary slightly depending on format and design)
Specifications:
Material: High-quality plastic or polyvinyl components
Atom sizes: varies to represent atomic radii or bonding distinctions
Connector types: rigid or flexible links for different bond angles and distances
Color scheme: standardized (e.g., black for carbon, red for oxygen, etc., or color-coded for lattice points)
Set contents: often includes 100–500+ components depending on model size
Models supported: SC, BCC, FCC, HCP, diamond, NaCl, CsCl, ZnS, etc.
Assembly tools: may include instruction manual and layout guide
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