high school part 1 /2 by ssl technologies physics ex-48 click part-1 /2 study the terminology of...

High School

Part 1 /2

by SSL Technologies

Physics Ex-48

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PART-1 /2

Study the terminologyof parabolic mirrors.

Light rays

Physics Ex-48

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RULES FOR DRAWING RAYS IN CURVED MIRRORS

A ray that is parallel to the principal axis is reflected through the principal focus (F).

A ray passing through the principal focus (F) is reflected parallel to the principal axis.

A ray passing through the center of curvature (C) is reflected back along its own path.

Note that images have properties called "characteristics".

Image characteristics include:

LocationLocation of image (behind mirror or in front of mirror) Size Size (magnification) of image (larger or smaller than object) AttitudeAttitude (whether the image is inverted or upright) ReversedReversed (whether the image is reversed left-to-right, "mirror image")

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CONCAVE MIRRORS

The characteristics of an image formed by a concave mirror dependon the location of the object. As it turns out, there are six “strategic”locations where an object may be placed. For each location, theimage will be formed at a different place and with differentcharacteristics. We will study the six different locations and labelthem as CASE-1 to CASE-6.

Case-1: Object at infinity

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Case-2: Object just beyond CCase-3: Object at C (center of curvature)

Case-4: Object between C and F

Case-5: Object at F (focal point)

Case-6: Object between F and V (within focal length)

Be sure to studyeach case!

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A ray parallel to the principal axis is reflected through the

focal point (F).

In order to draw images formed by curved mirrors, remember that :

FCPrincipal axis

Back of mirror

V

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A ray that goes through the focal point (F) is reflected parallel to

the principal axis.

In order to draw images formed by curved mirrors, remember that :

FCPrincipal axis

Back of mirror

V

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A ray that strikes the vertex (V) is reflected like a plane mirror. (Angle of

incidence = Angle of reflection)

In order to draw images formed by curved mirrors, remember that :

FCPrincipal axis

Back of mirror

V

Incident ray

Reflected ray

Incident ray

Reflected ray

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A ray that goes through C(the center of curvature) is reflected back

along its own path.

In order to draw images formed by curved mirrors, remember that :

FCPrincipal axis

Back of mirror

V

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This distance is known as the “focal length” (f).

fREMEMBER

The focal length (f) isfrom the focal point (F)to the vertex point (V).

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Due to the great distance the object is from the mirror,all rays arrive at the mirror parallel to the principal axis.

As a result, all rays focus at the focal point and no imageis formed.

Object at infinity No image

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Object just beyond C

Image is real,between C and F,

inverted and reduced.

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Object at C

Image is real, located at C, inverted and

same height as object.

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Object between C and F

Image is real, located beyond C, inverted and

larger than the object.

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Object at F

All rays are reflectedparallel and thus

no image is formed.

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Object between F and V(within the focal length)

Image is virtual, located inside the mirror,

upright and larger than the object.

Physics Ex-48

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Object

Image

An object is placed in frontof a concave mirror.

Find the location and characteristics of the image.

TASK

C

C

There are two steps in finding the image of a concave mirror.NOTE

Draw a ray parallel to the principal axisand make it reflect through the focal point.

Step-1Draw a ray through the focal point and

make it reflect parallel to the principal axis.

Step-2

Object pointIncident ray

Reflec

ted

ray

Incident ray

Reflected ray

Where the two reflected rays meet is the image point of the object point.

Image point

Characteristics of the image

~ Real (formed by reflected rays)

~ Inverted (upside down)

~ Smaller than the object

Rather than draw an actual

object, it is easier to draw

the object as an arrow.

This way, we can tell if the

image is inverted or not.

Such asright here!

We can now draw the image.

Since we are not given the location of the object, we can select any arbitrary location.

Since the intersecting rays are both reflected rays,the image is real.

Back ofmirror

Objects consist of an infinite number of points.

And each point has an infinite number of rays radiating outwards.

Images also consist of an infinite number of points.

Each point on the object has a corresponding point on the image.

In locating an image, we take one point on the object and find its corresponding point (location) on the image object.

As shown above, we usually take the (extreme) top point

and find its corresponding point on the image object.ClickClickClickClickClickClickClickClickClickClickClickClickClick

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For convex mirrors, the image is always virtual, always located inside the mirror,

always upright and always smaller than the object.

NOTE

Convex mirrors producea very large field of view.

Physics Ex-48Question-1

State the rules for finding the image formed by a curved mirror.

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1- A ray parallel to the principal axis is reflected through the focal point (F).

2- A ray through the focal point (F) is reflected parallel to the principal axis.

3- A ray through the center of curvature (C) is reflected back along its own path.

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Physics Ex-48Question-2

State four characteristics of images.

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1- Type (real or virtual)

2- Location (distance from mirror)

3- Magnification (size)

4- Attitude (upright or inverted

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Physics Ex-48Question-3

What is spherical aberration and how can it be eliminated?

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A fuzzy image produced by the fact that parallel rays do not passthrough the focal point (F).

It can be eliminated by making the mirror parabolic rather thanspherical.

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Physics Ex-48Question-4

The diagram below displays a concave mirror and a beam of lightstriking the mirror. Label each part.

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Focal plane

Principal axis

Reflected ray

Concave mirror

Vertex (V)

Focal point (F)

Physics Ex-48Question-5

The diagram below illustrates the image of an object producedby a concave mirror. Label the incident ray, the reflected rayand the extended ray.

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Extended ray

Incident ray

Reflected ray

Physics Ex-48Question-6

For each concave mirror below, draw the image.

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a)

Image

Image is real(formed by reflected rays)

Physics Ex-48Question-6

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b)

For each concave mirror below, draw the image.

Image

Image is real(formed by reflected rays)

Physics Ex-48Question-6

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c)

For each concave mirror below, draw the image.

Image

Image is real(formed by reflected rays)

Physics Ex-48Question-6

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d)

For each concave mirror below, draw the image.

Image

Image is virtual(formed by extended rays)

Physics Ex-48Question-7

The diagram below shows an illuminated object and its virtualimage in a concave parabolic mirror.

Determine the location of the focal point (F).

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C

F

REMINDERThe focal point (F) is half

the radius of curvature (C).

Physics Ex-48Question-8

The diagram below shows an object in front of a convex parabolicmirror. Draw the image.

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Image is virtual,upright and smaller

than the object.

Image

Physics Ex-48Question-9

Where must an object be placed in front of a concave mirror so as to form an image that is:

a) Smaller than object? ____________________________________

b) Inverted? ____________________________________

c) Virtual? ____________________________________

d) Inverted and magnified ? ____________________________________

e) Same height as object? ____________________________________

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Just beyond the center of curvature (C).

Beyond the focal point (F).

Within the focal length (f).

Between C and F.

At the center of curvature (C).

Physics Ex-48Question-10

Consider a convex mirror, where must an object be placedso as produce a real image?

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Impossible, convex mirrors do not produce real images.

Physics Ex-48Question-11

State the properties of a virtual image.

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A virtual image is formed by extended rays.

Physics Ex-48Question-12

In what important way does a virtual image differ from a real image?

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In the fact that a virtual image cannot be projected onto a screen.

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Physics Ex-48Question-13

Consider an object placed in front of a concave mirror. Which oneof the following statements correctly describes its image?

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A) It is in front of the mirror, inverted, real and smaller than the object.

B) It is behind the mirror, upright, virtual, and smaller than the object.

C) It is in front of the mirror, upright, real and smaller than the object.

D) It is behind the mirror, upright, virtual and larger than the object.

Image

Back

Physics Ex-48Question-18

An object is placed in front of a convex mirror as illustrated below.

Draw and label the light rays necessary to locate the image.

Incident ray

Reflected ray

Extended ray

Incident ray

Reflected ray

Extended ray

Image

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Image is virtual, upright and reduced.

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