Microscopes and Telescopes - Ray Optics and Optical Instruments

Microscopes:

• Simple microscope:

  • Magnifying power: Ability to magnify an object.

• Compound microscope:

  • Resolving power: Ability to distinguish between two closely spaced objects.
  • Total magnification: Product of the magnifying power of the objective lens and the eyepiece lens.

Telescopes:

• Refracting telescope:

  • Uses lenses to refract (bend) light.

• Reflecting telescope:

  • Uses mirrors to reflect light.
  • Newtonian telescope: Uses a parabolic primary mirror and a flat secondary mirror.
  • Cassegrain telescope: Uses a hyperbolic primary mirror and a parabolic secondary mirror.

• Magnification:

  • Ability to make an object appear larger.

Ray Optics:

• Laws of reflection:

  • Angle of incidence: Angle between the incident ray and the normal.
  • Angle of reflection: Angle between the reflected ray and the normal.
  • Normal: Perpendicular line to the surface at the point of incidence.

• Laws of refraction:

  • Angle of incidence: Angle between the incident ray and the normal.
  • Angle of refraction: Angle between the refracted ray and the normal.
  • Refractive index: Ratio of the speed of light in a vacuum to the speed of light in the medium.

• Total internal reflection:

  • Occurs when light strikes a boundary between two media with different refractive indices and is completely reflected back into the first medium.

Optical Instruments:

• Camera:

  • Pinhole camera: Simple camera that uses a small hole to project an image onto a surface.
  • Simple camera: Uses a lens to focus light onto a film or digital sensor.
  • SLR camera: Single-lens reflex camera that uses a mirror to reflect light from the lens to a prism, which then projects the image onto a focusing screen or film.

• Projector:

  • Slide projector: Projects images from slides onto a screen.
  • Overhead projector: Projects images from transparencies onto a screen.
  • Light travels from the back of the projector through the slide (for slide projectors) or the transparency (for overhead projectors)

• Spectrometer:

  • Instrument used to measure the wavelength of light.