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question_answer1) Directions : (Q. No. 1 to 5) Read the following text and answer the following questions on the basis of the same: Photocell: A photocell is a technological application of the photoelectric effect. It is a device whose electrical properties are affected by light. It is also sometimes called an electric eye. A photocell consists of a semi-cylindrical photo-sensitive metal plate C (emitter) and a wire loop A (collector) supported in an evacuated glass or quartz bulb. It is connected to the external circuit having a high-tension battery B and micro ammeter (µA) as shown in the Figure. Sometimes, instead of the plate C, a thin layer of photosensitive material is pasted on the inside of the bulb. A part of the bulb is left clean for the light to enter it. When light of suitable wavelength falls on the emitter C, photoelectrons are emitted. These photoelectrons are drawn to the collector A. Photocurrent of the order of a few microampere can be normally obtained from a photo cell. A photocell converts a change in intensity of illumination into a change in photocurrent. This current can be used to operate control systems and in light measuring devices. Photocell is an application of
question_answer2) Photosensitive material should be connected to
question_answer3) Which of the following statement is true?
question_answer4) The photocurrent generated is in the order of
question_answer5) A photocell converts a change in __ of incident light into a change in ____
question_answer6) Directions : (Q. No. 6 to 10) Read the following text and answer the following questions on the basis of the same: Electron Microscope Electron microscopes use electrons to illuminate a sample, hi Transmission Electron Microscopy (TEM), electrons pass through the sample and illuminate film or a digital camera. Resolution in microscopy is limited to about half of the wavelength of the illumination source used to image the sample. Using visible light the best resolution that can be achieved by microscopes is about ~200 nm. Louis de Broglie showed that every particle or matter propagates like a wave. The wavelength of propagating electrons at a given accelerating voltage can be determined by \[l=\frac{h}{\sqrt{2{{m}_{e}}v}}\] Thus, the wavelength of electrons is calculated to be 3.88 pm when the microscope is operated at 100 ke V, 2.74 pm at 200 ke V and 2.24 pm at 300 ke V. However, because the velocities of electrons in an electron microscope reach about 70% the speed of light with an accelerating voltage of 200 ke V, there are relativistic effects on these electrons. Due to this effect, the wavelength at 100 ke V, 200 ke V and 300 ke V in electron microscopes is 3,70 pm, 2.51 pm and 1.96 pm, respectively. Anyhow, the wavelength of electrons is much smaller than that of photons (2.5 pm at 200 ke V). Thus if electron wave is used to illuminate the sample, the resolution of an electron microscope theoretically becomes unlimited. Practically, the resolution is limited to ~0.1 nm due to the objective lens system in electron microscopes. Thus, electron microscopy can resolve subcellular structures that could not be visualized using standard fluorescences microscopy. In electron microscope, electron is used:
question_answer7) Who showed that electron also propagates like a wave?
question_answer8) Why electron as wave is used in electron microscope to illuminate the sample?
question_answer9) As the accelerating voltage increases, the wavelength of electron as wave
question_answer10) Wavelength of electron as wave at accelerating voltage 200 keV is
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