|
|
|
Optical
Instruments (Q) What is the meaning of "Parfocal" and is there any way to check if the Microscope used is Parfocal? (A ) To check if the microscope is parfocal a slide is selected which can be brought into a sharp focus using the microscope's most powerful objective. After that in descending order switching is done to the less powerful objectives. If a parfocal microscope is used, a slide which is in focus with a 40X objective will continue to be in focus with less powerful objectives also requring little or no adjustment. The question comes why to begin with the most powerful objective. This is because the focus range of the 40X objective is the narrowest. That is if a microscope is in focus at 40X, then it is quite sure that there would be no problem in focussing when switching over to other, less powerful objectives with wider focal ranges. (Q) How to differentiate between Fluorescent and Tungsten/Halogen Microscope Illuminators. (A) Generally standard student microscopes feature Tungsten or Halogen illuminators. It is only in the recent years that Fluorescent illuminators are used on microscopes. Tungsten or Halogen bulbs are known to provide a very bright, white light. As compared to Fluorescent bulbs, it has a different visual spectrum.Tungsten or Halogen are found to be extremely compatible with typical compound microscopes. On the downside both Tungsten as well as Halogen bulbs are prone to giving off substantial heat. Over time they are known to make the microscope base very hot. In contrast to them Fluorescent bulbs offers some benefits. They give off very little heat along with a long bulb life, that is something around 10,000 hours. On the flip side Fluorescent illuminated models are a bit costlier than the Tungsten/Halogen models. (Q) How is the magnification of Telescope Calculated ? (A ) For calculating the magnification, the Focal Length of the telescope is divided by the eyepiece diameter. To give an illustration a telescope that has a 900mm focal length and a 20mm eyepiece will have a magnification of 45X. (900/ 20 = 45). (Q) How to differentiate between a Reflecting and Refracting Telescope? (A) A Reflecting Telescope is also called as catoptric Telescope. A concave parabolic primary mirror is employed by the reflecting Telescope for collecting and focussing light onto a flat secondary mirror. The secondary mirror then reflects the image into an opening located at the side of the telescope and finally into the eyepiece assembly. On the other hand a Refracting Telescope also known by the name of Dioptric Telescope features a long thin tube. It is through this tube that the light passes in a straight line. The path followed by the light is from the front objective lens to the eyepiece located on the opposite end of the tube. (Q) What do the numbers 7x 35, 7x 50, 10x 50, etc. Indicate on Binoculars (A) The numbers that are seen on binoculars basically designate the magnification as well as objective lens size. To give an illustration, a reading of 7 x 35 in a binocular indicates that the binoculars will be able to magnify the image seven times, while 35 mm is the diameter of the front or objective lens. Similarly a Binocular which reads 7 x 50 has the capacity to magnify the image seven times, along with a 50 mm front lens diameter. It has been seen that larger front lenses means more light can enter thus making the binoculars suitable for viewing in low-light conditions. |
|
Miscellaneous
Lab Equipment (Q) What items can be considered as Electronic Laboratory Equipment? (A) Electronic laboratory equipment refers to the devices that contains electronic components like circuit boards, transistors etc. A word of caution while using electronic components. They can contain a high level of toxic materials like lead, silver etc. That is why they need to be recycled to prevent causing pollution to the enviroment. (Q) What is difference(if any) between a Spectrometer and a Spectrophotometer? (A ) Yes there is a difference. In case of spectrometers a prism or diffraction grating is used for focussing of the light. The light is then collected in a telescope for observance of its characteristics. On the other hand spectrophotometers work on the principle of use a diffraction grating for breaking white light into its component colors. To do this a diffraction grating is used. Consequently the fragmented colors are beamed through a cuvette. Cuvettes hold a solution under test. A photodetector is used to point out to the extent to which the light passes through the sample. Spectrophotometers find extensive application in the biology and chemistry for a correctly ascertaining the concentration of various substances. (Q) What is meant by diffraction Grating? (A) Diffraction grating is an optical device Diffraction gratings feature narrow slits or grooves which is engraved at equal intervals. Light gets fragmented into its component colours by these slits as they shine through the grating. Diffraction gratings provide a suitable alterrnative to prisms as they are cheap and easier to work with. (Q) How to differentiate between Carbon Zinc and Alkaline batteries? (A) Though Carbon Zinc and Alkaline cells both display a terminal voltage of nearly 1.5 Volts. The essential difference between the two lies in their capacity for producing sustained currents. In case of Carbon Zinc batteries, as current is taken, the terminal voltage drops. Though this takes place in Alkaline batteries too, but there is a gradual dropping (up to a point). (Q) What is the nature of Alcohol being used in an Alcohol Burner? (A) Ethanol is most popular. Ethanol is virtually a colorless flame. Ethanol Burner Fuels are now coming in with additives that add color to it. (Q ) Is there any need for Calibration of the Balances? (A) A new balance when it leaves the factory is always calibrated. This calibration sometimes may not stay stable due to shipping or long-term storage. To get over these problems it is always advised to do a periodical calibration of the balance. This is done using a weight of a known mass. The calibration is to be done strictly according to the manufacturer's manual. (Q) How to get optimum performance from a Van de Graaff Generator? (A) The following points may prove to be useful: - Cleaning the dome regularly reduces considerably the charge leakage. - Replacement of the dome in case it is pitted or dented. - Belt replacement in case it is worn or old. - Make sure that the combs positioned on the top and bottom of the generator is approximately 3/16" from the belt. - To cope up with the problem of humidity, blow-drying of the felt-covered pulley located on the bottom of the generator can be good idea. (Q) What is the most appropriate way to strike a Tuning Fork ( A ) Sometimes students not aware of the correct procedure strike a tuning fork in the wrong way. It is not uncommon to see students striking tuning forks by hitting them on the table. This is not to be done as it excites both the fundamental as well as higher harmonics of the vibrating bar. It is to be remembered that a tuning fork should be struck only on a rubber hammer or it could also be struck gently against the elbows. Whatever be the way the fork should be struck at end that is opposite the handle. (Q) What is the difference between Alnico and Neodymium Magnets ? (A) Mechanically strong Alnico magnets consist of aluminum, nickel, cobalt, copper along with iron. Alnico magnets display a high-residual magnetic field strength. Neodymium magnets on the other hand consist of neodymium, iron, boron, along with few other transition metals. As Neodymium is a rare earth material (It features in the Lanthanide series of the periodic table), these magnets are also called as Rare Earth Magnets. Neodymium magnets despite having the highest residual magnetic field strength is prone to brittleness as compared to other magnets. |
|
Lab
Safety (Q) What can be considered as an alternative to latex if someone is Allergic to it? (A) It is seen that a small percentage of people suffer allergic reaction to the latex protein in latex gloves. This allergy can range from contact dermatitis to even a hazardous attack. That is why disposable vinyl gloves or the disposable nitrile gloves have emerged as a suitable substitute to latex gloves. (Q) What are the types of Fire extinguisher used in the Laboratories ? (A) Fire extinguishers are mostly classified according to the type of fire they are supposed to extinguish. Class A Fire Extinguisher holds good for ordinary combustibles like paper, wood and some other plastics and textiles. Class B is useful for flammable liquid fires like alcohol. Class C Fire Extinguisher is applied in case of live electrical equipment fires, while class D Fire Extinguishers are used on combustible metals like sodium and magnesium. (Q) What are the types of Eyewash available in Labs? (A) If there is access to plumbing, as is the case with most laboratories, then eyewash should be connected permanently to the potable water source. In case there is no plumbing then gravity-feed eyewashes than can provide a continuous supply from a self-contained tank for around 15 minutes could be used. Personal self-contained eye wash bottles are also a good option in providing a prompt flushing at workstations. An important point to be kept in mind is that these wash bottles can at the most be a support to the plumbed or gravity-feed eye wash units and never thought of as a substitute. |
