Optical Instruments from Chapter Ray optics. Telescopes and Microscopes are explained., Slides of Physics

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OPTICAL

INSTRUMENTS

• M I C R O S C O P E
  • S I M P L E
  • C O M P O U N D
• R E F L E C T I N G T Y P E T E L E S C O P E
  • N E W T O N I A N T E L E S C O P E
  • C A S S E G R A I N T E L E S C O P E

SIMPLE MICROSCOPE

• (^) A simple microscope or a magnifying glass is a convex lens of short focal length that is held close to the eye.
• (^) A Virtual, Erect and Magnified image of the object is formed at the least distance of distinct vision from the eye held close to the lens.
• (^) Magnifying Power-

Least distance of distinct vision

AT NEAR POINT

BEYOND NEAR POINT ON USING CONVEX LENS

COMPOUND MICROSCOPE

Why a compound microscope? Formula for magnification: m=D/f In order to increase the magnification of an image, the focal length must decrease as they are inversely proportional. This does not give clear sharp images. The total magnification in a compound microscope is a function of the objective magnification multiplied by the eyepiece magnification. The advantage of having a compound lens system as opposed to a simple magnifier is that much higher magnifications can be achieved with two lenses rather than one A Compound microscope is an optical device used to see magnified images of tiny objects. The compound microscope can produce magnification of the order

TELESCOPES

• (^) A Telescope is an Optical Device which enables us to see distant objects clearly.
• (^) Broadly, there are 2 types of telescopes:

1. Refracting Telescope- Make use of lenses to view distant objects, includes- i)Astronomical Telescope and ii)Terrestrial Telescope
2. Reflecting Telescope- They make use of converging mirrors to view distant objects, they mainly include- i)Newtonian telescope and ii)Cassegrain telescope

Why a Reflecting Telescope?

• (^) Reflecting telescopes have many advantages over refracting telescopes. Mirrors don't cause chromatic aberration and they are easier and cheaper to build large.
• (^) A spherical mirror surface is relatively easy to make, but different parts of a spherical mirror have slightly different focal lengths, so images will be fuzzy. Mirrors in modern telescopes are made in various shapes to correct for these errors.

NEWTONIAN TELESCOPE

CASSEGRAIN TELESCOPE