Images formed by Mirrors and Lenses - Real and Virtual Images

Oct 25, 2026

Uploaded by Jacob

Covers how images are formed using mirrors and lenses, distinguishing real and virtual images by light behavior. Explains image formation with a plane mirror, concave and convex spherical mirrors, and the key ray-tracing rules for locating image points. Includes parabolic mirror focusing concepts and introduces the mirror equation with sign conventions for object and image distances. Extends to refraction-based imaging with converging and diverging lenses, describing how image type changes with lens-object distance and focal point.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages10

Reading Time25 min

AccessFree to download

Images

Image formation by mirrors

Images formed by lenses

| | | | | --- | --- | --- | | 4.1 Images formed by Mirrors and Lenses
• Images
• Image formation by mirrors
• Images formed by lenses | | | | Real Image | | --- | | diverging

Object

converging diverging

real Image | | Optical System
Light passes through the real image
Film at the position of the real image is exposed. | | Image formed by a plane mirror. | | --- | |
Object The virtual image is formed
directly behind the mirror.
Image
Light does not pass through the image | Object-Image • A physical object is usually observed by reflected light that diverges from the object. • An optical system (mirrors or lenses) can produce an image of the object by redirecting the light. – Real Image – Virtual Image Virtual Image Optical System diverging virtual Image Light appears to come from the virtual image but does not pass through the virtual image Film at the position of the virtual image is not exposed. Each point on the image can be determined by tracing 2 rays from the object. mirror B B’ A A’ object image p q A virtual image is formed by a plane mirror at a distance q behind the mirror. q = -p Parabolic Mirrors Parallel rays reflected by a parabolic mirror are focused at a point, called the Focal Point located on the optic axis. | Spherical mirrors
•Spherical mirrors are much easier to fabricate than parabolic mirrors
• A spherical mirror is an approximation of a parabolic mirror for small curvatures. (i.e. for paraxial rays –close to parallel to the optic axis.
• Spherical mirrors can be convex or concave | | | --- | --- | | light | | | concave convex | | | Ray tracing with a concave spherical mirrors
• A ray parallel to the mirror axis reflects through the focal point, F which is at a point half the radius distance from the mirror along the optic axis.
• A ray passing through the focal point reflects parallel to the mirror axis
• A ray striking the center of the mirror reflects symmetrically around the mirror axis
• A ray that passes through the center of curvature C reflects and passes back through itself | | | --- | --- | | | Law of Reflection | | Parabolic Reflector | | | --- | --- | | | | | Parabolic mirrors can be used to focus incoming parallel rays to a small area or to direct rays diverging from a small area into parallel rays. | | Parallel beams focus at the focal point of a Concave Mirror. | The position of the image can be determined from two rays from the object. | | --- | | | | When object distance > C
The image is real, inverted, reduced | | A concave mirror can form real and virtual images | | | | --- | --- | --- | | O > C
Real Inverted Reduced | C > O > F
Real Inverted Enlarged | F > O
Virtual Upright Enlarged | Question What image of yourself do you see when you move toward a concave mirror? Simulation of image formation by a mirror [http://qbx6.ltu.edu/s_schneider/physlets/main/opticsbench.shtml](http://qbx6.ltu.edu/s_schneider/physlets/main/opticsbench.shtml)[ ](http://qbx6.ltu.edu/s_schneider/physlets/main/opticsbench.shtml)[PHYSLETS were developed at Davidson University by Wolfgang Christian.](PHYSLETS were developed at Davidson University by Wolfgang Christian.) | A Convex Mirror always forms virtual images | | | --- | --- | | |
virtual, upright, reduced | Convex Mirror • Ray parallel to the optic axis reflects so that the reflected ray appears to pass through the focal point. Focal Point Image is virtual, upright, reduced Question Describe how your image would appear as you approach a convex mirror? Magnification q –positive – image is real M is negative-the image is inverted. Question A boy stands 2.0 m in front of a concave mirror with a focal length of 0.50 m. Find the position of the image. Find the magnification. Is the image real or virtual? Is the image inverted or erect? 1 1 1 ~~ ~~ + = ~~ ~~p q f

FAQs

What is the difference between a real image and a virtual image in mirrors?

A real image is formed where light actually converges and can expose film, while a virtual image appears to originate from behind the optical element and does not let light pass through the image location.

How do you determine the position of an image formed by a concave or convex mirror?

Use ray tracing: trace two rays from the object (e.g., rays related to the focal point and the center of curvature) and locate where they intersect for the real image or where they appear to diverge from for the virtual image.

How does a converging lens change an image as the lens is moved relative to the object?

A converging lens can form both real and virtual images, and at the focal point the image transitions from real to virtual when the lens-object relationship changes.

Oct 25, 2026

Uploaded by Jacob