This telescope, located on the summit of Hawaii

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• This telescope, located on the summit of Hawaiis
  dormant Mauna Kea volcano, is one of the largest
  telescopes in the United States.

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• Telescopes, microscopes, and cameras are all
  examples of optical instruments that enhance your
  ability to see.
• These optical instruments all use lenses or
  mirrors, or a combination of the two, to reflect
  and refract light.

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Telescopes
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Telescopes

• A telescope is an instrument that uses lenses or
  mirrors to collect and focus light from distant
  objects.

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Telescopes

• Reflecting Telescopes
• The reflecting telescope uses mirrors and convex
  lenses to collect and focus light.
• Light strikes a large concave mirror and is
  brought to a focus.
• This focused light is reflected in a mirror and
  forms a real image.
• A convex lens magnifies the image.

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Telescopes

• Refracting Telescopes
• The refracting telescope uses convex lenses to
  collect and focus light.
• Light from a distant object enters the telescope
  through a convex lens called the objective lens.
• The convex lens forms a real image inside the
  telescope.
• A convex lens magnifies this real image.

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Telescopes

1. The reflecting telescope uses a large concave
   mirror to focus the incoming light rays.

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Telescopes

1. The refracting telescope uses a series of lenses
   to focus light from distant objects.

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Cameras
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Cameras

• Pinhole Camera
• A simple pinhole camera can consist of a
  cardboard box with a small hole in one side.
• Light rays from the top and bottom of an object
  pass through the pinhole and cross paths.
• The rays form an upside-down, real image on the
  back wall of the box.

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Cameras

• Modern Film Camera
• In a modern film camera, the lens elements focus
  the incoming light rays, which pass through the
  diaphragm that controls the amount of light.
• The lens must move toward or away from the film
  to focus an object.
• The shutter opens and the focused rays strike the
  film.

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Cameras

• The focused light reacts with a light-sensitive
  chemical coating on the film that records the
  real image. The image is upside down and smaller
  than the object.

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Cameras

• In a single lens reflex (SLR) camera, the mirror
  reflects the image through the viewfinder. When
  the shutter release button is pushed, the mirror
  flips up. The focused light rays pass through the
  lens system to the film.

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Microscopes
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Microscopes

• A microscope is an optical instrument that uses
  lenses to provide enlarged images of very small,
  near objects. A compound microscope has two
  convex lenses.
• Light rays from below pass up through the object
  and then pass through a convex lens called the
  objective.
• The lens produces an enlarged, upside-down, real
  image.
• The eyepiece enlarges the image.

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Microscopes

• This compound microscope uses a mirror to reflect
  light up and into the microscope.

Eyepiece lens
Objective lens
Slide with specimen
Mirror
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Assessment Questions

• A refracting telescope collects and focuses light
  from distant stars with a
• convex lens.
• concave lens.
• convex mirror.
• concave mirror.

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Assessment Questions

• A refracting telescope collects and focuses light
  from distant stars with a
• convex lens.
• concave lens.
• convex mirror.
• concave mirror.ANS A

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Assessment Questions

• How is a camera brought into focus?
• The type of film or sensor is matched to the
  amount of light.
• Lenses are moved closer to or farther from the
  film or sensor.
• Lenses are moved closer to or farther from other
  lenses.
• The mirror changes the length of the light path
  in the camera.

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Assessment Questions

• How is a camera brought into focus?
• The type of film or sensor is matched to the
  amount of light.
• Lenses are moved closer to or farther from the
  film or sensor.
• Lenses are moved closer to or farther from other
  lenses.
• The mirror changes the length of the light path
  in the camera.ANS B