# 4.6.2.5

4.6.2.5 Lenses (physics only)

# 4.1.3 National and global energy resources

## Content

A lens forms an image by refracting light. In a convex lens, parallel rays of light are brought to a focus at the principal focus. The distance from the lens to the principal focus is called the focal length. Ray diagrams are used to show the formation of images by convex and concave lenses.

Content

Key opportunities for skills development

The image produced by a convex lens can be either real or virtual. The image produced by a concave lens is always virtual.

Students should be able to construct ray diagrams to illustrate the similarities and differences between convex and concave lenses.

The magnification produced by a lens can be calculated using the equation:

magnification = image heightobject height

Magnification is a ratio and so has no units.

Image height and object height should both be measured in either mm or cm.

In ray diagrams a convex lens will be represented by:

A concave lens will be represented by:

MS 5a, 5c WS 1.2

MS 3b, c

Students should be able to apply this equation which is given on the Physics equation sheet.

AT 4, 8

Investigate the magnification produced by a range of convex lenses.

WS 1.2 Use a variety of models such as representational, spatial, descriptive, computational and mathematical to solve problems, make predictions and to develop scientific explanations and understanding of familiar and unfamiliar facts.

AT4 Making observations of waves in fluids and solids to identify the suitability of apparatus to measure speed/frequency/wavelength. Making observations of the effects of the interaction of electromagnetic waves with matter (links to A-level AT i and j).

AT8 Making observations of waves in fluids and solids to identify the suitability of apparatus to measure the effects of the interaction of waves with matter (links to A-level AT h, j).

MS 5a Use angular measures in degrees

MS 5c Calculate areas of triangles and rectangles, surface areas and volumes of cubes

MS 3b Change the subject of an equation

MS 3c Substitute numerical values into algebraic equations using appropriate units for physical quantities

Resources

Video

Practicals

Demo:

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