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Mirrors

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Types of mirror There are two types of mirror Plane (flat) Curved
Concave (curves in) Convex (curves out)

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Plane Mirrors The image is Virtual (cannot be formed on a screen)
Laterally inverted Upright The same distance behind the mirror as the object is in front of the mirror

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Convex Mirrors The image is Virtual (cannot be formed on a screen)
Diminished (smaller) Upright

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Convex Mirrors Convex mirrors diverge parallel rays of light
The principal focus is always behind the mirror They have a wide field of view

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Concave Mirrors For distant objects the image is
Real (can be formed on a screen) Inverted Diminished (For near objects the image is upright, magnified and virtual)

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Concave Mirrors Concave mirrors converge parallel rays of light towards a principal focus inside the mirror

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Lenses

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Lenses Lenses are shaped pieces of glass which can be used to change the way we see things. Different types of lenses have different uses.

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Converging lenses

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Focus point – converging

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Converging lens Parallel rays of light are refracted through the principal focus of a convex lens. The distance from the principal focus to the centre of the lens is called the focal length.

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Images The image from a converging lens is: Inverted
Real (can be projected on a screen)

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Uses of converging lenses
The use of a converging lens depends on the nature of the image. The image depends on where the object is placed in relation to the lens Uses include cameras, the eye, projectors, magnifiers, specs, telescopes etc.

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Ray diagrams – camera Image is: Inverted Diminished Real

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Ray diagrams – Projector
Image is: Inverted Magnified Real

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Ray diagrams – magnifier
Image is: Upright Magnified Virtual

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Diverging lens

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Focus point – diverging

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Images The image from a diverging lens is: Upright Virtual Diminished

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Images Make sure that you can draw and recognise the ray diagrams for:
A camera A projector A magnifier Learn where the object and image are in relation to the focal length

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Refraction Light is slowed down or speeded up when it moves across the boundary into different media. Glass is more dense than air so the light slows down. As it does this it bends (refraction)

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Refraction The angle of refraction is always less than the angle of incidence. The emergent ray follows a path parallel to the incident ray

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Refraction The refraction takes place at the boundary of the two media. Some light is reflected at the boundary

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Refraction in a prism A prism is a shaped piece of glass which will disperse white light into its separate colours. The light is refracted twice, because it passes through 2 surfaces of glass

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Refraction in a prism Two prisms used together can return the spectrum to a single ray of white light. Make sure your ray diagrams clearly show the two areas of refraction

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