Converging lenses Diverging Lenses The Lens Equation We can make use of the fact that changing the focal length and position of the object we can change.

Converging lenses

Diverging Lenses

The Lens EquationWe can make use of the fact that changing

the focal length and position of the object we can change the size of the image created.

The lens maker equation relates the distance of the object and image with the focal length

Using the “thin lens” equation:A few rules are necessary to use the equation:

Object distances are always positiveImage distances are positive for real images

(when the image is on the opposite side of the lens as the object) and negative for virtual images (when the image is on the same side of the lens as the object).

The focal length is positive for converging lenses and negative for diverging lenses.

Thin Lens ExamplesA converging lens has a focal length of 20

cm. An object is located 50 cm from the lens. What type of image will be formed, and

where will it be located?

MagnificationMany applications of lenses involve

magnification.Magnification helps us see distant or

small objects.For Example: a toy is placed 8 cm in

front of a lens. An upright, virtual image of magnification 3 is seen. Where is the image located?

Applications of OpticsWhat common devices use lens or mirrors?

Overhead projectorTelescopeMicroscopeBinocularsCamerasEye glassesHuman eye

TelescopesTelescopes can be primarily composed of

refracting lenses or reflecting mirrors.

Simplistic Telescope Diagrams

Telescope Optics

Magnifying Glasses

What type of lens do you expect magnifying lenses use?

Overhead Projectors:

EyesEyes are complex

optical devices!Notice the blind spot?What would happen if

the focal point changed?

Corrective LensesEye glasses are used to ensure the image is

focused on the sensors at the back of the eye.

Binoculars

Gravitational LensingLenses can take other forms…. Including galaxies

or other massive objects.Objects with very high gravity bend light like a

lens. This can create optical illusions!