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# Spherical refracting surfaces - Six cases - PowerPoint PPT Presentation

Spherical refracting surfaces - Six cases. Sign Convention to be used in the optics equations: The object distance p is positive for a real object. It would be negative for a virtual object, but that is a rare situation.

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## PowerPoint Slideshow about ' Spherical refracting surfaces - Six cases' - buckminster-allen

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Presentation Transcript

• Sign Convention to be used in the optics equations:

• The object distance p is positive for a real object. It would be negative for a virtual object, but that is a rare situation.

• The image distance i is positive for a real image and negative for a virtual image.

• Radii of curvature get their sign based on whether the centers of curvature are on the “R-side” or “V-side”.

From posted “Practical Rules” on Lecture Materials page:

So

r < 0

R-side,

So

i > 0

V-side

R-side

So

r > 0

i > 0

Note: p > 0 since the object is real.

So

r < 0

i < 0

V-side

So

i < 0

R-side

R-side

So

r > 0

So

i < 0

R-side

So

r > 0

V-side

So

r < 0

i < 0

R-side

Focal point

Diverging Lens (f < 0)

f > 0

Focal point

f < 0

Diverging Lens

f > 0

Focal point

f < 0

Diverging Lens

V-side

V-side

R-side

R-side

V-side

Locating the Image

(From posted “Practical Rules” on Lecture Materials page)

Typical “near point”

Angular magnification

Not to scale.

s = “tube length”

The eyepiece acts as a magnifying glass for the image from the objective lens. The final magnification M is the product of the lateral magnification m of the objective lens and the angular magnification m of the eyepiece.

Refracting telescope

ey

Not to scale.

A distant object subtends an angle ob. The virtual image viewed through the telescope subtends ey.

myopic eye (shortsighted)

corrected with diverging lens

hyperopic eye (farsighted)

corrected with converging lens