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Unit 2: OpticsSection 5.3

Images in Curved Mirrors

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Concave mirrors have a reflecting surface that curves inward like the inside of a spoon.

Some common uses:◦ Shaving and makeup

mirrors◦ Reflectors in headlights◦ Dentist mirrors

Concave Mirrors

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Like plane mirrors, curved mirrors reflect light according to the law of reflection.

However, because concave mirrors are curved, they reflect in a certain way – they will converge.

Concave Mirrors

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Concave mirrors can produce many different kinds of images. According to SPOT:◦ Size – same, smaller, or larger.◦ Position – same, closer, or farther away.◦ Orientation – upright or inverted.◦ Type – real or virtual

The image characteristics depend on where you place the object in front of the mirror. ◦ We will look at 3 different cases.

Concave Mirrors

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Ray Diagrams – Key Parts Before we determine the

image characteristics for concave mirrors you need to know some key parts of the ray diagram.

◦ Principal Axis – A line that is normal (perpendicular) to the center of a mirror.

◦ Vertex – The point at which the principal axis meets a mirror.

◦ Focal Point – The point at which converging light rays meet.

Focal point

Vertex

Principal Axis

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When drawing ray diagrams, there are 3 main rules you must follow:

◦ Draw an incident ray traveling parallel to the principal axis. It will reflect through the focal point .

◦ Draw an incident ray passing through the focal point on the way to the mirror. It will travel parallel to the principal axis upon reflection.

◦ Draw an incident ray travelling to the vertex. It will reflect back at the same angle (relative to the principal axis) with which it entered the mirror (Law of Reflection).

Ray Diagrams - *Rules* (See p.198-199)

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Object Between the Focal Point and the Mirror

Ray Diagrams – Concave (Case 1)

Image Properties

Size

Position

Orientation

Type

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Object Between the Focal Point and Two Times the Focal Point

Ray Diagrams – Concave (Case 2)

Image Properties

Size

Position

Orientation

Type

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Object Beyond Two Times the Focal Point

Ray Diagrams – Concave (Case 3)

Image Properties

Size

Position

Orientation

Type

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Check this out:◦ http://physics.gac.edu/~chuck/PRENHALL/Chapter

%2026/AABXTES0.html

Concave Mirror Animation

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A mirror that is curved outward, like the outside of a bowl, is called a convex mirror.

Common Uses:◦ Security mirrors in stores◦ Sunglasses◦ Side mirrors on vehicles

Convex Mirrors

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The curved surface of a convex mirror causes light rays to travel away from each other, or diverge.

These rays will never meet in front of the mirror as they do in concave mirrors.

However, if you extend the rays behind the mirror, they will intersect at the focal point, F.

Convex Mirrors

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When drawing ray diagrams for concave mirrors, the image depended on where you put the object with reference to the focal point.

In convex mirrors, since the focal point is behind the mirror there is only one case – the object in front of the mirror!

Ray Diagrams – Convex Mirrors

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Object in Front of the Mirror

Ray Diagrams – Convex

Image Properties

Size

Position

Orientation

Type

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Check this out:◦ http://physics.gac.edu/~chuck/PRENHALL/Chapter

%2026/AABXTER0.html?I1.x=32&I1.y=25

Convex Mirror Animation

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P.209: #2, 10, 12, “Pause and Reflect” Common Place Book:

◦ Definitions: “Key Terms” on p.196.◦ Tic-Tac-Toe:

For anyone wanting to complete the case study option, read, summarize, and answer the questions on p.208. The article is called “Curved Surfaces Collect Solar Energy”.

Assignment (Part C – Sec 5.3)