MICROSCOPY
BRIGHT FIELD, DARK FIELD AND PHASE CONTRAST
MICROSCOPE

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

 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

Working principle
Of
Bright field microscope

Oil immersion :

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

Working principle
Of
Dark field
microscope

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

Working principle
Of
Phase contrast
Microscope