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Slide 1
Slide 2
Lenses A transparent object used to change the path of light
Examples: Human eye Eye glasses Camera Microscope Telescope Reading
stones used by monks, nuns, and scholars ~1000 C.E.
Slide 3
Lenses THERE ARE ALWAYS TWO REFRACTIONS IN A LENS
Slide 4
Lenses Two basic shapes Converging lens Diverging lens
Slide 5
Converging Lens A lens that has its thickest part in the middle
Causes all incident parallel rays to converge at a single point
after refraction
Slide 6
Converging Lens OPTICAL CENTRE: the exact centre of the
lens
Slide 7
Ray diagrams for Converging Lenses
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Images through Converging Lenses Lets practice
Slide 10
Images in Convex lens vu f Image Real, inverted & highly
diminished Image formed in convex lens when the object is placed at
infinity FF 2F Use As a camera lens when object is very far,
burning lens
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object Images in Convex lens vu f Image Real, inverted &
diminished Image formed in convex lens when the object is placed
beyond 2f FF 2F Use As a camera lens when object is not very
far
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Image formed in convex lens when the object is placed at 2f
object Image Real, inverted & same size as object Images in
Convex lens vu f FF 2F Use In terrestrial telescope for erecting
the image
Slide 13
Image formed in convex lens when the object is placed between f
and 2f object Image Real, inverted & magnified Images in Convex
lens vu f FF 2F Use Cinema and slide projectors
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Image formed in convex lens when the object is placed at the
focus object Image At Infinity, inverted and highly magnified
Images in Convex lens u f FF 2F Use In collimator of a spectrometer
to obtain parallel beam
Slide 15
Image formed in convex lens when the object is placed between
the Focus and optical centre object Images in Convex lens u f Image
Virtual, magnified & upright FF 2F Use As a reading glass
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Converging Lenses Can produce real and virtual images The size
and attitude will vary depending on the location of the object Many
uses including to correct for far-sightedness
LocationSizeAttitudeLocationType Beyond 2F
SmallerInvertedBehindReal At 2F SameInvertedBehindReal Between 2F
and F LargerinvertedBehindReal At F No clear image Inside F
largeruprightIn frontVirtual Object Image
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Diverging Lens A lens that has its thinnest part in the middle
Causes all incident parallel light rays to spread apart after
refraction
Slide 18
Diverging Lens
Slide 19
Ray diagrams for Diverging Lenses
Slide 20
Slide 21
Images through Diverging Lenses Lets practice
Slide 22
Diverging Lenses Only produce virtual images that are always
smaller, upright and in front of the lens Used to correct
near-sightedness (can see objects close up)
Slide 23
Image formed in concave lens when the object is placed at
infinity Images in Concave lens Image Virtual, erect &
diminished f FF 2F Use In Galilean telescope
Slide 24
Image formed in concave lens when the object is placed in front
of lens object Images in Concave lens Image Virtual, erect &
diminished v u f FF 2F Use In spectacles for correcting
short-sightedness