1. EXTENDING HUMAN VISION

2. Extending Human Vision
With light, mirrors, and lenses, we have been able to make microscopes and telescopes
Microscopes and telescopes have allowed us to see and learn new things
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Microscopes
A compound light microscope uses two convex lenses to magnify small, close objects.
Magnify means to make the image look larger than the real size.
To focus the image, the object is moved closer to or farther away from the object lens.
Adjusting the distance to make the image clear is called focusing.
light reflects off the mirror, through the object, though the objective lens and eyepiece lens, into the eye
See pages
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4. the objective lens has a fixed focal point
if an object is between 1-2 focal lengths away from the lens, the image is enlarged
the eyepiece lens magnifies the image (10X), and the objective lens magnifies it again (usually 4X, 10X, 40X)

5. Telescopes
Help us see objects that are too far away to be seen clearly with the naked eye.
Far away objects appear dim because less light enters your eye.
Two main types of telescopes:
Refracting and Reflecting Telescopes

6. Refracting Telescope

7. Refracting Telescopes
uses two lenses:
a convex objective lens to collect and focus light from a distant object,
a convex eyepiece lens to magnify the image.
It needs very large lenses! Sometimes, they are too big:
Heavy
Distort image
Expensive
Difficult to make
See page 219
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8. Problems with Refracting Telescopes
Large objective lenses tend to flex, due to their own weight which can distort the image.
Glass lenses, even of the highest quality, absorb some of the light and are expensive.
It needs very large lenses! Sometimes, they are too big:
Heavy
Distort image
Expensive
Difficult to make
See page 219
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10. Reflecting Telescopes
TWO mirrors (plane and concave) and a convex lens:
Light enters the telescope and is reflected off a concave mirror at the bottom.
A plane mirror reflects the light towards the eyepiece
A convex lens in the eyepiece magnifies the image.
Most large telescopes, like those used in space, are reflecting telescopes.
the light reflects off the concave mirror and strikes a plane mirror at an angle before it converges to its focal point
the light reflects into the eyepiece, which is a convex lens that magnifies object
some telescopes collect light rays using several mirrors and then combine the rays into a single image (e.g. The Keck Telescope)
See page 220
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11. The Hubble Space Telescope – is a Reflecting
Earth’s atmosphere blurs the image of distant objects in space, just like water blurs your vision
to overcome this blurry effect, some telescopes are placed in space
The Hubble Space Telescope was launched into outer space in it is a reflecting telescope that uses two mirrors.

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Binoculars
Binoculars are actually two refracting telescopes mounted side by side.
To shorten the length of the tubes in binoculars, prisms are used to reflect the light back and forth.
thumbscrews on binoculars are used to change the focal length in order
to focus on the object being
viewed
See page 221
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14. Cameras

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Cameras
Light enters the camera through an opening called the aperture.
Light then passes through a lens which focuses the image on the light detector.
A telephoto lens
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Camera Lenses
Wide-angle lens allow for a wide field of view.
Telephoto lenses allow distant object to appear larger.
A telephoto lens
See page 222
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17. Cameras Have Similarities to Human Eyes
Eyelid
Iris
Retina
Rods and cones
Camera
Lens cap
Diaphragm
Charge-coupled device(CCD)
pixels
See page 223
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18. How to Bring an Image into Focus
to focus properly, the screen that is receiving the image must be the correct distance from the lens (where the light rays converge)
if the screen is too close or too far from the lens, the image will appear blurry
this is similar to near-sightedness and far-sightedness

19. Lasers only one wavelength
all of the light rays move in the same direction,
laser light can travel great distances without spreading out and can contain a lot of energy.
and the crests and troughs line up.

20. Because laser light contains only one wavelength- it does not make a rainbow

21. Lasers and Laser Surgery
Lasers can be used in surgery in place of scalpels.
Remove cataracts
Reattach retinas
Laser eye surgery to reshape the cornea.
stop bleeding
Laser surgery
See page 224
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Eye surgery video
Animation:
Real:
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Optical Fibres
Optical fibres are transparent glass fibres that can transmit light from one place to another using total internal reflection.
Total internal reflection is when light strikes a boundary between two materials and is totally reflected.
Optical fibre
See page 225
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Take the Section 6.2 Quiz

24. Optical Fibres are used for
Medical procedures (orthoscopic surgery)
Telecommunications (telephone, internet, video)
Optical fibre
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Homework
Complete WS
Read Eye Dissection in text p 212
Watch Eye Dissection Video:
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