Mirror and Lens Review

Diverging and Converging

Diverging Converging

• Convex lens

• Concave mirror

• Concave lens

• Convex mirror

Uses of Mirrors and Lens

• Concave mirror – makeup mirror, mirror dentist uses to magnify your teeth

• Convex mirror – rear-view mirror, mirror shopkeeper uses in corners to produce a wider image of his store

• Concave lens – used on the back of buses to see more out of the back; corrects nearsightedness

• Convex lens – magnifying lens; used to correct farsightedness

Definitions to Know

• Converging – come together

• Diverging – spread apart

• Reflection – bounce off

• Refraction – bending due to a change in speed

• Focal Point – the point where light rays meet

• Real Image – formed when light rays come together; can be viewed on a screen

• Virtual Image – formed behind mirrors; when light rays diverge

Specular vs. Diffuse Reflection

Specular

• Light rays reflect parallel

• Will form an image

Diffuse

• Light rays reflect in many directions

• No image is formed

Law of Reflection

• States the angle of incidence is EQUAL to the angle of reflection

Images formed by Mirrors

Concave Mirrors

• Real images – far away from mirror (outside f)

• No image – at f

• Virtual images – close to the mirror (between f and the mirror)

Convex Mirrors

• Always forms virtual images

Images formed by Lenses

Convex Lenses

• Real images – far away from lens (outside f)

• No image – at f

• Virtual images – close to the lens (between f and the lens)

Concave Lenses

• Always forms virtual images

real, inverted, reduced

real, inverted, same

real, inverted, magnified

NO IMAGE

virtual, upright, magnified

virtual, upright, reduced

Mirror Diagram

real, inverted, reduced

real, inverted, same size

real, inverted, magnified

NO IMAGE

virtual, upright, magnified

virtual, upright, reduced

Lens Diagrams

More on Refraction• Refraction occurs because light changes speed when it enters a new medium

• Less dense to more dense – light will slow down and bend toward the normal

Example: air to water

• More dense to less dense – light will speed up and bend away from the normal

Example: glass to air

Total Internal Reflection• Only can occur when light travels from a more dense to less dense medium

• Used in fiber optics technology

Mirror/Lens Math

𝑑𝑖 = (𝑓−1 − 𝑑0−1)−1

Determine the image distance when an object is placed 30 cm from a concave mirror with a focal length of 10 cm.

𝑑𝑖 = (10−1 − 300−1)−1

𝑑𝑖 = 15 𝑐𝑚