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# Converging Lenses - PowerPoint PPT Presentation

Converging Lenses. Section 4.6 Lesson 13. Uses for lenses. Lenses. A lens is a thin transparent piece of glass or plastic that has at least one curved side The sides can be concave, convex or both. Lenses. A lens changes the direction in which light

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Converging Lenses

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## Converging Lenses

Section 4.6

Lesson 13

### Lenses

• A lens is a thin transparent piece of glass or plastic that has at least one curved side

• The sides can be concave, convex or both

### Lenses

• A lens changes the direction in which light

• If the light rays come together it is a converging lens, if the rays move apart it is a diverging lens

### Our eyes have lenses

• Our eye uses a lens to focus an image of an object on the retina of the eye

• The brain then interprets that image (one more “flip”)

### Vision correction using lenses

Diverging lens – used to correct short-sightedness

Converging lens – used to correct farsightedness

### Converging lens

• Because light can travel in both directions through a lens there are two focal points – one on either side of the lens

Draw a straight line through the centre of the converging lens – this is the axis of symmetry

principalaxis

F

F1

### Drawing Ray Diagrams

• Step 1

• Draw a straight line (the axis of symmetry) through the centre of the lens perpendicular to the principal axis

• An incident ray drawn parallel to the principal axis will refract through the focus on the other side of the lens

For an object beyond 2F1

principalaxis

F

2F1

F1

### Drawing Ray Diagrams

• Step 2

• Draw an incident ray through F1 that will refract through the lens parallel to the principal axis

principalaxis

F

F1

### Drawing Ray Diagrams

• Step 3

• An incident ray aimed at the centre of the lens will pass through the lens

principalaxis

F

F1

Identify the characteristics of this image:

principalaxis

F

F1

closer

inverted

smaller

real

L: _____________ O: _____________ S: ____________ T: ________

### Notes

• Complete the handouts:

• 4.6 Converging Lenses: Drawing Ray Diagrams

• 4.6 What are lenses and what are some of their applications? (Summary)

### Vocabulary Journal

• Add this term and definition:

• lens