Topicm863b7f26d25550b7_1528449000663_0Topic

How the image is formed using diverging lenses? Virtual focal pointvirtual focal pointVirtual focal point

Levelm863b7f26d25550b7_1528449084556_0Level

Second

Core curriculumm863b7f26d25550b7_1528449076687_0Core curriculum

IX. Optics. The student:

8) constructs diagrams of the images formed by the lens; distinguishes real, virtual, upright, inverted images; compares the size of the object and image.

Timingm863b7f26d25550b7_1528449068082_0Timing

45 minutes

General learning objectivesm863b7f26d25550b7_1528449523725_0General learning objectives

Reconstructs images of objects formed by a diverging lensdiverging lensdiverging lens.

Key competencesm863b7f26d25550b7_1528449552113_0Key competences

1. Analyses the position of an image with respect to the lens.

2. Recognises the characteristics of an image formed by the diverging lensdiverging lensdiverging lens.

Operational (detailed) goalsm863b7f26d25550b7_1528450430307_0Operational (detailed) goals

The student:

- reconstructs images of objects formed by a diverging lensdiverging lensdiverging lens with respect to the position of an object,

- determines the characteristics of images formed by a diverging lens with respect to the position of an object.

Methodsm863b7f26d25550b7_1528449534267_0Methods

1. Discussion.

2. Experiment.

Forms of workm863b7f26d25550b7_1528449514617_0Forms of work

1. Individual work.

2. Group work.

Lesson stages

Introductionm863b7f26d25550b7_1528450127855_0Introduction

Revision:

- Enumerate the parameters describing the lens.

- What characteristics has an image formed by a converging lens?

Procedurem863b7f26d25550b7_1528446435040_0Procedure

diverging lensdiverging lensdiverging lens is curved inwards on both sides. It is represented on diagrams by the symbol.

[Ilustration 1]

Construction rules for a diverging lens.

[Ilustration 2]

Rule 1.
A ray parallel to the optical axis is refracted by the diverging lens in such a way that its extension intersects the optical axis at the virtual focal point.
m863b7f26d25550b7_1527752263647_0Rule 1.
A ray parallel to the optical axis is refracted by the diverging lens in such a way that its extension intersects the optical axis at the virtual focal point.

[Ilustration 3]

Rule 2.
A light ray, which extension intersects the optical axis at the focal point, is refracted by the diverging lens in such a way that it travels parallel to the optical axis.
m863b7f26d25550b7_1527752256679_0Rule 2.
A light ray, which extension intersects the optical axis at the focal point, is refracted by the diverging lens in such a way that it travels parallel to the optical axis.

[Ilustration 4]

Rule 3. 
The direction of a light ray passing through the optical centreoptical centreoptical centre of the lens stays unchanged.

Task
Make appropriate constructions and examine the characteristics of an image formed by a diverging lensdiverging lensdiverging lens for different positions of an object and fill in the table below. What difference have you noticed while you compare results for converging and diverging lenses?

[Illustration interactive]

[Table 1]

Solution:
[Table 2]

Lesson summarym863b7f26d25550b7_1528450119332_0Lesson summary

For diverging lens the images are always virtual, upright and reduced.m863b7f26d25550b7_1527712094602_0For diverging lens the images are always virtual, upright and reduced.

Selected words and expressions used in the lesson plan

concave lensconcave lensconcave lens

diverging lensdiverging lensdiverging lens

optical axisoptical axisoptical axis

optical centreoptical centreoptical centre

parallel rayparallel rayparallel ray

reduced imagereduced imagereduced image

refracted rayrefracted rayrefracted ray

upright imageupright imageupright image

virtual focal pointvirtual focal pointvirtual focal point

virtual imagevirtual imagevirtual image

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virtual focal point1
virtual focal point

ognisko pozorne

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diverging lens1
diverging lens

soczewka rozpraszająca

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optical centre1
optical centre

środek optyczny

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concave lens1
concave lens

soczewka wklęsła

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optical axis1
optical axis

oś optyczna

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parallel ray1
parallel ray

promień równoległy

Rayri4GYWNlAj1
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reduced image1
reduced image

obraz pomniejszony

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refracted ray1
refracted ray

promień załamany

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upright image1
upright image

obraz prosty

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wymowa w języku angielskim: upright image
virtual image1
virtual image

obraz pozorny

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wymowa w języku angielskim: virtual image