Light, Lenses, and Mirrors

37
W. Sautter 2007

description

Use principles of reflection and refraction to describe how lenses and mirrors work. **More good stuff available at: www.wsautter.com and http://www.youtube.com/results?search_query=wnsautter&aq=f

Transcript of Light, Lenses, and Mirrors

Page 1: Light,  Lenses, and  Mirrors

W. Sautter 2007

Page 2: Light,  Lenses, and  Mirrors

The next slide is a quick promo for my books after which the presentation will begin

Thanks for your patience!Walt S.

[email protected] stuff at: www.wsautter.com

Page 3: Light,  Lenses, and  Mirrors

Books available at:www.wsautter.com

www.smashwords.comwww.amazon.com

www.bibliotastic.comwww.goodreads.com

Walt’s Books for Free!

Page 4: Light,  Lenses, and  Mirrors

NormalLine

NormalLine

i

r i

r

Glassn = 1.5

Airn =1.0

r = angle of refraction

i = angle of incidence

Light travels more slowlyin glass than air and

bends towards the normalwhen entering glass from air

Light moving fromglass to air

increases speedand bends awayfrom the normal

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Virtual focusFocus = -

Can form only virtual,Erect and reduced

images

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Principlefocus

Parallel rays

Focus = +Can form real images(enlarged or reduced

& inverted) orEnlarged virtual images

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NormalLine

r i

Incidentray

Reflectedray

Mirror surface

Angles are ALWAYS measured from the NORMAL LINE

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Parallel rays

Reflected rays

RealFocus

Focal length = +Forms real, inverted,Reduced or enlarged

Image. Also formsVirtual, erect,

Enlarged images.

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Parallel rays

Reflected rays

Virtual focus

Focal length = -Forms only virtual,

erect, reduced images betweenthe virtual focus and the mirror.

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Waves from aDistant source = crest

= trough

Barrier withTwo slits

In phase wavesEmerge from slits

Constructive interference

Destructiveinterference

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Wavelength

Frequency

Velocity Wavelength

Frequency

Velocity

vx =

Page 12: Light,  Lenses, and  Mirrors

VISIBLE AND INVISIBLE LIGHT• MOST “LIGHT” IS NOT VISIBLE TO THE HUMAN EYE !

• ONLY ABOUT 7 % OF THE KNOWN KINDS OF LIGHT CAN BE SEEN WITHOUT SPECIAL INSTRUMENTATION.

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POTASSIUM METALBATTERY

VOLTMETERPHOTONS

PICKUP

WIREELECTRONS

ONLY CERTAIN MINIMUM FREQUENCIES OF LIGHT

FREE THE ELECTRONS FROM THE METAL

(ONLY PHOTONS WITH ENOUGH ENERGY)

THE PHOTOELECTRIC EFFECT EXPERIMENT

Page 14: Light,  Lenses, and  Mirrors

Parallel ray

Focal rayRay thru 2f focus (f)2 fvertex

Reflects thruThe focus

Reflects parallelTo principal axis

Principal axis

Reflects Back Into itself

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Parallel ray

Focal rayRay thru 2f f2 f

Image is:RealInvertedReducedAppears between f & 2f

Object beyond 2f

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Image is:RealInvertedSame sizeAppears at 2f

Parallel rayFocal ray

ray thru 2f f2 f

Object at 2f

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Image is:RealInvertedEnlargedAppears beyond 2f

Parallel ray

ray thru 2fFocal ray

2 f f

Object betweenf and 2f

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Image is:VirtualErectEnlargedAppears behind the mirror

Parallel ray

ray thru 2f

Foc

al r

ay

2 f f

ray thru 2f

ApparentConvergence

Of rays

Object inside focus

Page 19: Light,  Lenses, and  Mirrors

Angle of incidence = Angle of Reflection For each ray

Dotted lines Shows the Apparent

Ray source

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Parallel rays

Reflected rays

Virtual focus

Focal length = -Forms only virtual,

erect, reduced images betweenthe virtual focus and the mirror.

Dotted lines Shows the ApparentRay focus

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Apparent Convergence of rays

2 f(f)

Focal ray

Parallel rayRay thru 2f

Image is:VirtualErectReducedAppears behind the mirror

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focus (f)focus (f) 2 f2 fx x x x

Parallel rayPasses thruThe focus

Focal rayRefracts parallelTo principal axis

A ray thru theCenter of the

lenses

Remains unbent

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Parallel ray

focus (f)focus (f) 2 f2 fx x x x

Focal ray

Image is:RealInvertedReducedAppears between f and 2f

Object beyond 2f

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focus (f)focus (f) 2 f2 fx x x xFocal ray

Parallel ray

Image is:RealInvertedSame sizeAppears between f and 2f

Object at 2f

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focus (f)focus (f) 2 f2 fx x x xFocal ray

Parallel ray

Image is:RealInvertedEnlargedAppears beyond 2f

Object betweenf and 2f

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focus (f)focus (f) 2 f2 fx x x x

Image is:VirtualErectEnlargedAppears on sameSide as Object

ApparentConvergence

Of rays

ObjectInsidefocus

Page 27: Light,  Lenses, and  Mirrors

focus (f) 2 f2 f focus (f)

Apparent ray convergenceIs on same side as object

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f2 f f 2 fFocal ray

Parallel ray

Ray thru center

Image is:VirtualErectReducedAppears on sameSide as object

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Wave A

Wave A

Wave A

Wave B

Wave B

Wave B

Constructive interference

Destructive interference

Partially Constructive interference

Page 30: Light,  Lenses, and  Mirrors

Waves from aDistant source

= crest = trough

Barrier withTwo slits

In phase wavesEmerge from slits

Constructive interference

Destructiveinterference

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d

0

1

1

2

2

m

SPECTRAL

ORDER

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m = spectral order The bright central band is zero and each bright band

to the right or left is counted by consecutive integers 1,2,3 etc.

d = distance separating the slits (meters)= wavelength of light in meters

= angle between the zero band and the spectral band m

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Each edge of the slit creates a new wave front. The

two new waves then interfercreating a diffraction pattern

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m = spectral order The bright central band is zero and each dark band

to the right or left is counted by consecutive integers 1,2,3 etc.

s= slit width (meters)= wavelength of light in meters

= angle between the zero band and the spectral band m

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