The document discusses three types of microscopes: bright field, dark field, and phase contrast. A bright field microscope uses a condenser and objective lenses to illuminate specimens from below and view them with high magnification. Dark field microscopy uses a special condenser to prevent direct illumination, making the background dark and allowing specimens to be seen by light they scatter. Phase contrast microscopy was developed by Frits Zernike and uses special lenses to increase contrast by converting phase differences in light waves to amplitude differences, allowing unstained living cells to be viewed.

1. MICROSCOPY
BRIGHT FIELD, DARK FIELD AND PHASE CONTRAST
MICROSCOPE

2. BRIGHT FIELD MICROSCOPE :
 Compound student microscope
 Mechanical parts :
 Base – horse shoe shaped
 Pillar
 Inclination joint arm or limb
 Stage – stage clip to fix slide
 Sub stage – carries condenser
 Body tube
 Coarse and Fine adjustments
 Revolving nose piece

3.  Optical parts :
 Objective – Low power(10x), High dry(45x), Oil immersion(100x)
 Eye piece – Monocular, Binocular
 Condenser – condense light cone shape, control light intensity,
iris diaphragm to regulate light
 Mirror – lens with one plane and one concave surface
attached to pillar
focus in three directions

4. Working principle
Of
Bright field microscope

5. Oil immersion :

6. DARK FIELD MICROSCOPE :
 Specimen (illuminated), Background (dark)
 Special condenser – prevents parallel and oblique rays to enter objective,
thus making the field dark
 Absence of specimen – dark
 Presence of specimen – scatter rays and specimen gets illuminated
 Maximum magnification – 1500x
 Resolution – 0.1 – 0.2 m
 Used for finding cells in suspension

7. Working principle
Of
Dark field
microscope

8. PHASE CONTRAST MICROSCOPE :
 Discovered by Frits Zernike in 1930’s
 Special condenser, objective and magnifier
 Change in phase increase the contrast of image
 Used to study unstained / living cells
 Resolving power – 0.1 – 0.2 m

9. Working principle
Of
Phase contrast
Microscope