Physics 1161 PreLecture 17 Refraction of Light Lenses

$Physics 1161: Pre-Lecture 17 Refraction of Light Lenses • sections 26 -3 – 26$

$Light Doesn’t Just Bounce It Also Refracts! Reflects: Bounces qi = qr qi qr$

$Index of Refraction 186, 000 mi/s (3 x 108 m/s): it’s not just a$

$Indices of Refraction$

Snell’s Law When light travels from one medium to another the speed changes v

Three Rays to Locate Image • Ray parallel to axis bends through the focus.

Characterizing the Image • Images are characterized in the following way 1. Virtual or

Object Beyond 2 f • Image is – Real – Inverted – Reduced

Object at 2 f • Image is – Real – Inverted – Same size

Object Between 2 f and f • Image is – Real – Inverted –

Object Closer than F • Image is – Virtual – Upright – Enlarged

$Concave (Diverging) Lens • Ray parallel to axis refracts as if it comes from$

Image Formed by Concave Lens • Image is always – Virtual – Upright –

Concave Lens Image Distance • As object distance decreases – Image size increases

Image Characteristics • CONVEX LENS – IMAGE DEPENDS ON OBJECT POSITION – Beyond F:

Lens Equations do di • convex: f > 0; concave: f < 0 •

Slides: 21

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$Physics 1161: Pre-Lecture 17 Refraction of Light Lenses • sections 26 -3 – 26$

Physics 1161: Pre-Lecture 17 Refraction of Light Lenses • sections 26 -3 – 26 -5

$Light Doesn’t Just Bounce It Also Refracts! Reflects: Bounces qi = qr qi qr$

Light Doesn’t Just Bounce It Also Refracts! Reflects: Bounces qi = qr qi qr Refracts: Bends q 1 q 2 n 1 n 2 n 1 sin(q 1)= n 2 sin(q 2)

$Index of Refraction 186, 000 mi/s (3 x 108 m/s): it’s not just a$

Index of Refraction 186, 000 mi/s (3 x 108 m/s): it’s not just a good idea, it’s the law! Speed of light in vacuum Speed of light in medium Index of refraction so always!

$Indices of Refraction$

Indices of Refraction

Snell’s Law When light travels from one medium to another the speed changes v = c/n, but the frequency is constant. So the light bends: n 1 sin(q 1)= n 2 sin(q 2)

Shape of a Lens

Types of Lenses

Lens Terms

Three Rays to Locate Image • Ray parallel to axis bends through the focus. • Ray through the focus bends parallel to axis. • Ray through center of lens passes straight through.

Characterizing the Image • Images are characterized in the following way 1. Virtual or Real 2. Upright or Inverted 3. Reduced, Enlarged, Same Size

Object Beyond 2 f • Image is – Real – Inverted – Reduced

Object at 2 f • Image is – Real – Inverted – Same size

Object Between 2 f and f • Image is – Real – Inverted – Enlarged

Object at F • No Image is Formed!

Object Closer than F • Image is – Virtual – Upright – Enlarged

Converging Lens Images

$Concave (Diverging) Lens • Ray parallel to axis refracts as if it comes from$

Concave (Diverging) Lens • Ray parallel to axis refracts as if it comes from the first focus. • Ray which lines up with second focus refracts parallel to axis. • Ray through center of lens doesn’t bend.

Image Formed by Concave Lens • Image is always – Virtual – Upright – Reduced

Concave Lens Image Distance • As object distance decreases – Image size increases

Image Characteristics • CONVEX LENS – IMAGE DEPENDS ON OBJECT POSITION – Beyond F: Real; Inverted; Enlarged, Reduced, or Same Size – Closer than F: Virtual, Upright, Enlarged – At F: NO IMAGE • CONCAVE LENS – IMAGE ALWAYS SAME – Virtual – Upright – Reduced

Lens Equations do di • convex: f > 0; concave: f < 0 • do > 0 if object on left of lens • di > 0 if image on right of lens otherwise di < 0 • ho & hi are positive if above principal axis; negative below