Practical 4Topic

: Microscopes and telescopesPurpose: To determine the conditions essential for increasing the magnification power of both the astronomical telescope and compound microscope. Activity 1: Building a simple astronomical telescope.

Theoretical

knowledge: A telescope is an instrument designed for the observation of remote objects by the collection of electromagnetic radiation. The first known practically functioning telescopes were invented in the Netherlands at the beginning of the 17th century. "Telescopes" can refer to a whole range of instruments operating in most regions of the electromagnetic spectrum.

The name "telescope" covers a wide range of instruments and is difficult to define. They all have the attribute of collecting electromagnetic radiation so it can be studied or analyzed in some manner. The most common type is the optical telescope; other types also exist and are listed below.

An optical telescope gathers and focuses light mainly from the visible part of the electromagnetic spectrum (although some work in the infrared and ultraviolet). Optical telescopes increase the apparent angular size of distant objects as well as their apparent brightness. In order for the image to be observed, photographed, studied, and sent to a computer, telescopes work by employing one or more curved optical elementsusually made from glasslenses, or mirrors to gather light and other electromagnetic radiation to bring that light or radiation to a focal point. Optical telescopes are used for astronomy and in many non-astronomical instruments, including: theodolites (including transits), spotting scopes, monoculars, binoculars, camera lenses, and spyglasses. There are three main types:

The refracting telescope which uses lenses to form an image.

The reflecting telescope which uses an arrangement of mirrors to form an image.

The catadioptric telescope which uses mirrors combined with lenses to form an image.

Other optical telescopes:

Infrared telescopes Submillimetre telescopes Ultraviolet telescopes Fresnel Imager

For your information, Galileos telescope was a refracting telescope. Isaac Newton, who was born the same day Galileo died, invented another kind of telescope, called a reflecting telescope. Reflecting telescopes use mirrors instead of lenses to make faraway things look bigger. Reflecting telescopes can be made much more powerful than refractors, and Newtons invention paved the way for all the great telescopes to come.How ItWorks

Light enters through the front objective lens and then passes through the eyepiece lens before reaching your eye.

by David Garrison

Refracting telescopes depend on one amazing fact. As light passes through glass, it slows down. Slowing down a light beam makes it bend. Why? Imagine youre pulling a wagon along a sidewalk, when the wheels on one side slip off into the grass. The wheels turn slower in the grass than they do on the sidewalk, and the wagon moves toward the grass. In the same way, when a light beam passes through a glass lens inside a telescope, it moves toward the lens. When the light beam comes out the other side, its bent!

The shape of the lens means light near the top of the lens is bent down and light near the bottom of the lens is bent up. Somewhere inside the tube the light beams cross, but before they can spread out again the eyepiece lens bends the light beams again and sends them to the eye.

Because the light beams cross, the image ends up upside-down. This doesnt matter much when youre looking at Mars or the Moon (remember theres no real up or down in space), but refracting telescopes used to see objects here on Earth often have another set of lenses to flip the image right-side up again.

In a reflecting telescope, light bounces off mirrors instead of passing through lenses.

by David Garrison

Refracting telescopes are simpler than reflecting telescopes, but they have an important limitation. Remember that the light passing through the glass lens gets bent. It turns out that different colours are bent different amounts, and that causes the light to become unfocused. Isaac Newton solved this problem by replacing the lenses with mirrors.

When light hits a mirror, it doesnt bend. Instead, it bounces off. Just like a ball bouncing off a wall, a light beam comes off a mirror the same way it comes in. In other words, the angle in equals the angle out. And that rule is true for all the light, no matter its colour.

The primary mirror in a reflecting telescope is curved just the right amount to bounce all the light onto the secondary mirror. From there, the light passes through the eyepiece lens, which bends the light into the eye.

Telescope Facts

Probably the worlds most famous telescope today is the Hubble Space Telescope. It is a reflecting telescope that orbits 600 kilometres above the Earth. Because it is above the Earths atmosphere, Hubble is able to see faraway objects more clearly than any telescope in history.

The Very Large Array is a radio astronomy observatory in New Mexico.

By Jonathan Larsen

Telescopes arent limited to just the light we can see. Invisible kinds of light, like radio waves and x-rays, are important to astronomers, too. Every time astronomers use a new kind of light to look at the universe, they make new and unexpected discoveries. When scientists first used x-rays to look at the sky, they discovered black holes. When they used radio waves, they found the light left over from the birth of the universe, the event called the Big Bang.

X-ray telescopes are some of the strangest devices ever invented. Because x-rays are so powerful, theyd pass right through any mirror they hit straight on. To capture x-rays, scientists use the same effect you use when you skip a rock across a pond. The x-rays come in at an angle, hitting the mirror with a glancing blow that focuses them onto the detector. To increase the number of x-rays collected, the telescopes are built like nested barrels, with the insides of the barrels all covered in mirrors.

Materials: Mounting rod, plasticene, lens holders, convex lenses (+ 2.5 D, + 7 D, + !4 D, + 20 D)

Procedures:

1. We are given converging lenses of different focal length. With the help of diagram, we have described how we had set up a simple astronomical telescope. 2. Our simple astronomical telescope was build and tested out by focusing on a distant object. The magnification or our telescope was determined.

3. How can you increase the magnification of your telescope? Test out your idea.

Result

: Pictures of our telescope

1. We have using the +2.5 D convex lens with its holder. It is attached at the mounting rod by using the plasticene. For your information, the lens was acts as object lens.

2. After that, we have used another +20 D convex lens with its holder is attached at the end of the same mounting rod by using the plasticene. This lens was acts as eye lens.

3. In making a telescope, we need to make sure that the focal length for the object lens is longer than the focal length of the eye lens. The focal length that we have used here is 50 cm for objective lens and 10 cm for eye lens.

4. Our metric card is used to be as the material that observed by the set up telescope.

5. The image that resulted from the observation is virtual, inverted to the metric card and is magnified. We have used the formulae below in this experiment:

m = fo / fe= 50 cm / 10 cm

= 56. The magnification power of telescope can be increased by using shorter focal length of eye lens and longer focal length for object lens.Activity 2: Building a compound microscope

Theoretical

knowledge: A microscope is an instrument to see objects too small for the naked eye. The science of investigating small objects using such an instrument is called microscopy. Microscopic means invisible to the eye unless aided by a microscope.

An early microscope was made in 1590 in Middelburg, Netherlands. Two eyeglass makers are variously given credit: Hans Lippershey (who developed an early telescope) and Hans Janssen. Giovanni Faber coined the name for Galileo Galilei's compound microscope in 1625. (Galileo had called it the "occhiolino" or "little eye".)

The first detailed account of the interior construction of living tissue based on the use of a microscope did not appear until 1644, in Giambattista Odierna's L'ochio della mosca, or The Fly's Eye.

It was not until the 1660s and 1670s that the microscope was used seriously in Italy, Holland and England. Marcelo Malpighi in Italy began the analysis of biological structures beginning with the lungs. Robert Hooke's Micrographia had a huge impact, largely because of its impressive illustrations. The greatest contribution came from Antoni van Leeuwenhoek who discovered red blood cells and spermatozoa. On 9 October 1676, Leeuwenhoek reported the discovery of micro-organisms.

The most common type of microscopeand the first inventedis the optical microscope. This is an optical instrument containing one or more lenses producing an enlarged image of an object placed in the focal plane of the lenses.

"Microscopes" can be separated into optical theory microscopes (Light microscope), electron microscopes (e.g.,TEM), and scanning probe microscopes (SPM). Optical microscopes function through the optical theory of lenses in order to magnify the image generated by the passage of a wave through the sample, or reflected by the sample. The waves used are electromagnetic (in optical microscopes) or electron beams (in electron microscopes). Types are the compound light, stereo, and the electronic microscope.

Optical

Optical microscopes, using visible wavelengths of light, are the simplest and most used. Optical microscopes have refractive glass and occasionally of plastic or quartz, to focus light into the eye or another light detector. Mirror-based optical microscopes operate in the same manner. Typical magnification of a light microscope, assuming visible range light, is up to 1500x with a theoretical resolution limit of around 0.2 micrometres or 200 nanometers. Specialized techniques (e.g., scanning confocal microscopy, Vertico SMI) may exceed this magnification but the resolution is diffraction limited. The use of shorter wavelengths of light, such as the ultraviolet, is one way to improve the spatial resolution of the optical microscope, as are devices such as the near-field scanning optical microscope.Sarfus, a recent optical technique increases the sensitivity of standard optical microscope to a point it becomes possible to directly visualize nanometric films (down to 0.3 nanometer) and isolated nano-objects (down to 2nm-diameter). The technique is based on the use of non-reflecting substrates for cross-polarized reflected light microscopy.

CBP Office of Field Operations agent checking the authenticity of a travel document at an international airport using a stereo microscopeUltraviolet light enables the resolution of microscopic features, as well as to image samples that are transparent to the eye. Near infrared light images circuitry embedded in bonded silicon devices, as silicon is transparent in this region. Many wavelengths of light, ranging from the ultraviolet to the visible are used to excite fluorescence emission from objects for viewing by eye or with sensitive cameras.

Phase contrast microscopy is an optical microscopy illumination technique in which small phase shifts in the light passing through a transparent specimen are converted into amplitude or contrast changes in the image. A phase contrast microscope does not require staining to view the slide. This microscope made it possible to study the cell cycle.

The traditional optical microscope has been recently modified into a digital microscope, where instead of directly viewing the object, a charge-coupled device (CCD) camera projects the image to a monitor.

Electron

Three major variants of electron microscopes exist:

Scanning electron microscope (SEM): looks at the surface of bulk objects by scanning the surface with a fine electron beam and measuring reflection. May also be used for spectroscopy. See also environmental scanning electron microscope Transmission electron microscope (TEM): passes electrons completely through the sample, analogous to basic optical microscopy. This requires careful sample preparation, since electrons are scattered so strongly by most materials. This is a scientific device that allows people to see objects that could normally not be seen by the naked or unaided eye.

Scanning Tunneling Microscope (STM): is a powerful technique for viewing surfaces at the atomic level.

The SEM and STM can also be considered examples of scanning probe microscopy.

Materials: Mounting rod, plasticene, lens holders, convex lenses (+ 2.5 D, + 7 D, + !4 D, + 20 D)Procedures:

1. We are given converging lenses of different focal lengths. With the help of a diagram, we had described on how we set up a compound microscope.2. Our compound microscope was build and tested out by focusing on a tiny object. The magnification of our compound microscope has been determined. 3. How can you increase the magnification power of the compound microscope? Test out your idea. Result

:

Picture of microscope

1. We have used the plasticine, a convex lens +20 D for this experiment. The convex lens which is +20 D was placed at the mounting rod by using the plasticine. This lens work as an object lens.

2. We also have used another convex lens which is +14 D to attached at the other end of the rod by using the plasticine that have been prepared for us. This lens acted as eye lens.

3. For your information, the focal length of the eye lens is greater than the object lens.

4. The focal length for the eye lens is 7 cm and 5 cm for object lens.

5. In testing the efficient of our telescope, we have used a piece of graph paper with a number of 8 to be observed under the microscope.

6. The image that resulted is virtual, inverted and magnified.

7. We have used the formulae below in getting the best result or image:M= h I2 / h 0

= 7 cm / 5 cm

= 1.4

8. We can increase the magnification power by making a longer focal length of eye lens and shorter focal length of the object lens.

Conclusion: As a conclusion, the telescope and the microscope that we have built is efficient as it would. This is because we have used the right lens as the focal lens and the object lens.

Discussion:

1. Change in direction, or bending of a wave, at the boundary between two media is called refraction.

2. In this experiment, there were using the concept of refraction. It happen when we used the lens.

3. First thing that we should know in this experiment is about the concept of the lens that we have used.

4. When light strikes a surface along the perpendicular, the angle of incidence is zero, and the angle of refraction will also be zero. The refracted ray leaves perpendicular to the surface and does not change direction.

5. Snells law has stated that the ratio of the sine of the angle of incidence to the site of the angle of refraction is a constant. For light going from the vacuum into another medium, the constant, n, is called the index of refraction. Snells law, is written as n = sin i / sin r6. For lenses, we develop a sense of signs in our mathematics. It comes from the direction that light travels through the lens. In the diagram which follows, note that the positive sense of things occurs when light starts on one side and converges on the other.

Object distance is positive Object distance is negative (very rare)

Image distance is negativeImage is uprightImage is reduced (concave)or enlarged (convex)Image is virtual Image distance is positiveImage is invertedImage is realImage can be enlarged or reduced

Focal point is negativeLight rays are diverged by lens Focal point is positiveLight rays are converged by lens

7. From the experiment, we have known that there were two types of convex lenses. They object lens and eye lens. For telescope, eye lens must be lower power and longer focal length, while objective lens has high power and short focal length.

8. Eye lens is the lens that been used so that our eyes can see trough the telescope meanwhile objective lens is a lens where the view of object get through the telescope. This meant that it is a situated opposite of eye lens.9. The eye lens work as the magnification lens and it can be adjusted so that the image, I1 can be at the position less than fm. 10. The image that formed by eye lens is virtual, inverted to the object and is magnified.

11. The light ray from the far object is almost parallel when reach to the object lens. The image that formed is real, inverted and diminished at the focal point of the object lens.

12. The formulae for the distance between object lens and eye lens is fo + fm, If the distance of the lenses are greater than (fo + fm), there is no image formation.

13. Compound microscope consisted of two convex lenses which using the high power. But, both lenses have short focal length.

14. We must concern for the lens position. We must also make sure that lens which near to the object is the object lens with focal length fo. So, the object should be positioned between fo and 2fo.

15. Object lens produce real, inverted and magnified image.

16. Eye lens magnifies the image I1. The final image I2 that produce by the eye lens is virtual, inverted to the object and is magnified.

17. Focal length for the eye lens fe is greater than fo. The first image I1 should be located between lens centers and focus point of the eye lens.18. We also must have several steps for the precaution in doing this experiment such as we must be careful while handling the lens so that the lens would not be broken. Questions:

1. State the functions of both the objective and eye lenses of the astronomical telescope.

Objective lens function in receive light ray from the object while eye lens magnifies the image produced by the objective lens.2. How do you increase the magnification power of both the astronomical telescope and compound microscope?Magnification power for telescope can be increased by using the eye lens. The focal length of the eye lens must be longer while the objective lens must have short focal length. Magnification power for the microscope can be increased by using objective lens with longer focal length and eye lens with short focal length.3. What precautions have you taken in undertaking the above projects? Why?

We must make sure that the distance between both lenses is not exceeding (fo + fm). This is because; there will be no image formation, if the distance is exceeding it. Mastery of Knowledge and Skills Questions:

1. At the end of the practical, answer the following questions:

a) What have you learnt from the practical?

After doing the practical, I have learnt many things that I event know about it before this. First of all, I have learnt about the basic concepts of microscope and telescope. Both of them were using the same lens which is convex lens. Besides that, I have also learnt about the steps in making a telescope and microscope in the simple way. From this, I have known how the telescope and microscope was built. For me, it is a really good thing for us to know about it. This is because; we can apply this application in anything that we want to use it. Last but not least, I also have learnt about finding the best magnification by using the calculation or graphing. I also have known on how to find the appropriate focal length for concave and convex lens in both telescope and microscope. b) Which part of the primary science curriculum teaches this particular topic?

Level II (Year 4 to Year 6); Investigating the Earth and the Universe; Investigating Technology; Technology. c) Discuss how you can use the above practical in your teaching and learning?

I will use the above practical in my class so that there will be hands- on activities in my class. This is because the students will be easily to remember and understand by doing the activities by themselves. I also will ask them to do this type of practical so that they will be more understood on this topic. So, as a teacher I must use any style or tactic in my teaching process so that the students will understand about this topic and also can applied those concept that they have learnt in the topic in their daily life. d) What was the role of the teacher in the above practical?

In this practical, they were student centered which means that the teacher just act like a facilitator to help them whenever they have any problems. The teacher also can guide them while doing the experiment so that there will be no problems and also can get the accurate result or answer. Resources:

http://en.wikipedia.org/wiki/Telescope.10.29 pm. 11 April 2010http://en.wikipedia.org/wiki/Microscope.10.29 pm. 11 April 2010http://nobelprize.org/educational_games/physics/microscopes/1.html.10.29 pm. 11 April 2010http://nobelprize.org/educational_games/physics/microscopes/about.html.10.29 pm. 11 April 2010http://inventors.about.com/od/mstartinventions/a/microscope.htm.10.29 pm. 11 April 2010http://science.howstuffworks.com/telescope.htm.10.29 pm. 11 April 2010http://www.yesmag.ca/how_work/telescope.html.10.29 pm. 11 April 2010Paul W. Zitzewitz; PhD. Physics Principles and Problems. Glencoe McGraw- Hill