Microscopes & Telescopes By Dr. Karamjit Singh Senior Lecturer

1. Microscopes & Telescopes By Dr. Karamjit Singh Senior Lecturer Govt. Polytechnic College For Girls Patiala email:karamjit_gpw@yahoo.com Mobile:- 9914029020; 9501029020

2. The History • Many people experimented with making microscopes • Was the microscope originally made by accident? (Most people were creating telescopes) • The first microscope was 6 feet long!!! • The Greeks & Romans used “lenses” to magnify objects over 1000 years ago.

3. Hans and Zacharias Janssen of Holland in the 1590’s created the “first” compound microscope • Anthony van Leeuwenhoek and Robert Hooke made improvements by working on the lenses Hooke Microscope Anthony van Leeuwenhoek 1632-1723 Robert Hooke 1635-1703

4. The Father of Microscopy • Anton van Leeuwenhoek (1632 – 1723) • he taught himself new methods for grinding and polishing tiny lenses of large curvature • these magnifications of up to 270 diameters • he was the first to see and describe bacteria, yeast plants and the circulation of blood corpuscles in capillaries.

5. Why do we need microscopes? • Not everything we want to see is visible to the naked eye. • Microscopes uses lenses to brighten and enlarge nearby and very small objects.

6. The “First” Microscope Zacharias Jansen 1588-1631

7. Microscope One or more lense that makes an enlarged image of an object.

8. Evolution of the microscope Choice of lens magnification 2 set lenses

9. Types of Microscopes • Simple • Compound • Stereoscopic • Electron

10. Simple Microscope • Similar to a magnifying glass and has only one lens.

11. So, a convex lens of short focal length can be used to see magnified image of a small object and is called simple microscope. Principle When a small object is placed between optical centre and focus of a convex lens, its virtual, erect and magnified image is formed on the same side of the lens. The image is formed at the least distance of distinct vision from the eye.

13. Working Let AB be an object placed between the points F and C. Its virtual image A’B’ will be formed on the same side of the object. The position of object AB is so adjusted that the image A’B’ is formed at the least distance of distinct vision (D).

14. Magnifying Power It is defined as the ratio of the angle subtended by the image at the eye to the angle subtended by the object seen directly, when both lie at the least distance of distnict vision. Magnifying power, M = As angles α and β are small, these angles can be replaced by their tangents.

15. From right angled triangle CA’Q From right angled triangle CAB

18. So, we see that lesser is the focal length of the convex lens used as simple microscope, greater is the value of the magnifying power.

19. What is a compound light microscope? • Mechanism for enlarging an image

20. Compound Microscope Lets light pass through an object and then through two or more lenses.

21. Compound Microscope

22. Construction and Ray Diagram A compound microscope consists of two convex lenses separated by a certain distance. Lens towards the object is called objective and lens towards the eye is called eye piece. The objective is a convex lens of very short focal length and is placed close to the object. The eye piece is also a convex lens but of slightly longer focal length and is held close to the eye. The object AB to be examined is placed just beyond the principal focus F1 of the objective which produces its real, inverted and magnified image A’B’. The position of eye piece is adjusted so that A’B’ lies between the optical centre C2 and principal focus F2 of the eye piece. Thus, the eye piece acts as a magnifying glass, A²B² is formed at the distance of distinct vision and this final image is seen by the eye.

23. PrincipleWhen the object is placed just beyond the focus of a convex lens, a real, magnified and inverted image is formed. This image may be seen through another convex lens using it as a simple magnifying glass. Such a combination of the lenses produces a microscope of large magnifying power.

24. MagnifyingPowerofCompoundMicroscope The ratio of the angle subtended by the final image to that subtended by the object at the eye when both are placed at the distance of distinct vision.

26. How Does a Microscope Work? the specimen the image the eye Each lens magnifies the image, increasing its overall size A lens is a bi-convex disk that bends light The bent rays produces an image The farther the light rays are bent, the larger the image appears

27. How Does a Microscope Work? the specimen the image the eye The image is always seen upside down and backwards from its actual position

28. Ocular Lens (Magnifies Image) Objective Lens (Gathers Light, Magnifies And Focuses Image Inside Body Tube) Body Tube (Image Focuses) • Bending Light: The objective (bottom) convex lens magnifies and focuses (bends) the image inside the body tube and the ocular convex (top) lens of a microscope magnifies it (again).

29. Ocular Lens Body Tube Nose Piece Arm Objective Lenses Stage Stage Clips Coarse Adj. Diaphragm Fine Adjustment Light Source Base Skip to Magnification Section

30. Uses Microscopes have been and are being used in many different areas, such as: • identifying minerals • solving crimes • see how freezing affects food • study human cells • find the cause of diseases • discovering where illegal drugs are grown

31. A paramecium http://www.microscope-microscope.org/gallery/Mark-Simmons/pages/paramecium2.htm

32. A green protist http://www.microscope-microscope.org/gallery/Mark-Simmons/pages/the_fish.htm

33. Stereoscopic Microscope Gives a three dimensional view of an object. (Examples: insects and leaves)

34. Electron Microscope Uses a magnetic field to bend beams of electrons; instead of using lenses to bend beams of light.

35. Electron Microscopes • The electron microscope (EM) uses a beam of electrons, which results in better resolving power than the light microscope. • Magnify up to 100,000 times • Distinguish between objects 0.2 nanometers apart • Scanning electron microscopesexamine cell surfaces. • Transmission electron microscopes(TEM) are useful for internal details of cells.

37. 10 m Human height 1 m Length of some nerve and muscle cells 10 cm Unaided eye Chicken egg 1 cm Frog eggs 1 mm 100 mm Plant and animal cells Light microscope 10 mm Nucleus Most bacteria Mitochondrion 1 mm Smallest bacteria Electron microscope 100 nm Viruses Ribosomes 10 nm Proteins Lipids 1 nm Small molecules Atoms 0.1 nm

39. Telescopes • It is an instrument for seeing distant objects clearly and magnified. It is of two types: 1. Astronomical telescope A telescope used to see heavenly bodies. It produces a virtual and inverted image. 2. Terrestrial telescope It is used for observing objects on earth. It would be necessary to have an erect image. A telescope used for observing objects on earth is called a terrestrial telescope.

40. History • Hans Lippershey Middleburg, Holland • invented the refractor telescope in 1608 • Galileo • the first to use a telescope in astronomy. Galileo's designs used a combination of convex and concave lenses. • Kepler • improved the design to have two convex lenses, which made the image upside-down. Kepler's design is still the major design of refractors today, with a few later improvements in the lenses and the glass to make them.

41. Galileo Galilei (1564-1642)

42. History • invented by Dutch lens maker in 1608 • Galileo: small 30X scope • Observed the moon and “began” the modern age of Astronomy where measurement was more important than philosophy

43. Galileo noticed • moons orbiting Jupiter • phases of Venus • craters on the moon • sunspots This was strong evidence that Copernicus was right although Galileo wasn’t willing to die for it.

44. Why can’t you see an object that is far away? The answer is simple: the object does not take up much space on your eye’s screen (retina). Using a digital camera analogy, at 150 feet the writing on a dime does not cover enough pixels on your retinal sensor for you to read the writing. This can be corrected by bending the light with lenses.

45. The lens in your eyes works like a glass lens. The light bends as it goes through a different medium. • Light rays are bent when they intersect glass; a curved surface can produce an image. • In your eye, the image is then focused at the retina.

46. How does this apply to telescopes? • If you had a bigger eye, you could collect more light from the object. This image could be magnified so it stretches out over more pixels in your retina. • In a telescope, two pieces make this possible: • the objective lens (refractor telescopes) or primary mirror (reflecting telescopes) • the eye piece

47. The objective lens (in refractors) or primary mirror (in reflectors) collects lots of light from a distant object and brings that light, or image, to a point or focus. • An eyepiece lens takes the bright light from the focus of the objective lens or primary mirror and "spreads it out" (magnifies it) to take up a large portion of the retina. This is the same principle that a magnifying glass (lens) uses; it takes a small image on the paper and spreads it out over the retina of your eye so that it looks big.

49. When you combine the objective lens or primary mirror with the eyepiece, you have a telescope. Again, the basic idea is to collect lots of light to form a bright image inside the telescope, and then use something like a magnifying glass to magnify (enlarge) that bright image so that it takes up a lot of space on your retina.

50. A telescope has two general properties • how well it can collect the light (the aperature) • how much it can magnify the image (the magnification)