Simple & compound microscope PPT

microscope ppt

1. Simple & Compound Microscope Presented by- MAAZ UL HAQ C.L G upta eye institute

2. Microscope A n optical instrument used for viewing very small objects, such as mineral samples or animal or plant cells, typically magnified several hundred times . TYPES: Simple microscope Compound microscope

3. Simple Microscope A simple microscope is nothing but a single biconvex lens. It is referred to as magnifying glass The object to be viewed through a simple microscope is placed between the optic center and the focus Image formed by a simple microscope is erect, virtual and magnified.

4. Linear magnification Height of Image image distance = = Height of Object object distance Angular magnification Angle subtended at the eye by the image formed at the distance of distinct vision Magnifying Power = Angle subtended at the eye by the object formed at the distance of distinct vision

5. Magnifying Power of a Simple Microscope The magnifying power or angular magnification of a microscope may be defined as the: Ratio of the angle subtended at the eye by the image formed at the distance of the distinct vision to the angle subtended by the object when placed at the distance of the distinct vision.

6. The ray diagram shows that the image of the object AB is formed at A1B1. A1B1 is formed at the least distance of distinct vision. The figure shows that the angle A 1 OB 1 subtended at the eye by the object in the position A 1 B 1 is greater than the angle AOB subtended by it in the position AB. From this it is clear that the eye estimates the angle subtended by an object on it and not the linear size of the object.

7. Uses: A simple microscope is used as a magnifying glass. It cannot be used to observe very tiny objects like bacteria and cells because of its low magnification.

8. COMPOUND MICROSCOPE It is an optical device used to see highly magnified image of tiny objects. Construction:   It consist of two convex lenses of short focal length arranged co-axial at the free end of tube, at a suitable fixed distance . Objective Lens: It is a convex lens of very short focal length f o and small aperture, kept near the object . Eye piece: It is also a convex lens of comparatively larger focal length f e and larger aperture kept near the eye

9. Optics of Compound Microscope The object AB is placed at u o slightly larger than the focal length of objective lens . The objective lens forms a real, inverted and magnified image A’B’ of the object AB on the other side of lens . The distance between the objective and eyepiece is so adjusted that the image A’B’ lie within the focus of eyepiece. This image A’B’ acts as an object for eyepiece. The eyepiece E form a virtual and magnified final image A”B” which is inverted to object.

10. Magnifying power of a compound Microscope Magnifying power = The ratio of the angle subtended at the eye by the final virtual image , to the angle subtended at the eye by the object Where , β = angle subtended at the eye by final image α = angle subtended at the eye by object . h ’ = height of image , h = height of object U e = Object distance from eye piece, D = least distance of distinct vision m o = Magnification of Objective lens, m e = magnification of Eyepiece lens tan θ= perpendicular / base

11. The eye piece acts as a simple microscope . where D = distance between eye piece to final image and f e = focal length of eye piece . As u o = -f o v o = L =Length of microscope tube.