Determination of the focal length of a converging lens

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Wilfred Lyons
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الهيئة األكاديمي ة المشتركة قسم: العلوم المادة: الفيزياء الشهادة: المتوسطة نموذج رقم 4 المد ة: ساعة واحدة نموذج مسابقة )يراعي تعليق الدروس والتوصيف المعد ل للعام الدراسي 207-206 وحتى صدور المناهج

1 الهيئة األكاديمي ة المشتركة قسم: العلوم المادة: الفيزياء الشهادة: المتوسطة نموذج رقم 4 المد ة: ساعة واحدة نموذج مسابقة )يراعي تعليق الدروس والتوصيف المعد ل للعام الدراسي وحتى صدور المناهج المطو رة( This test includes four mandatory eercises in two pages. The use of non-programmable calculators is allowed. Eercise (5 points) Determination of the focal length of a converging lens In a lab session, we have a converging lens, a luminous object of height 2 cm and a screen. The aim is to determine the focal length of. We place the object at a distance d from the lens. We note that when the distance D between the object and the screen is 90 cm, we obtain on the screen a sharp image of height 4 cm. The figure (Doc ) below shows the object, its real image '' and the optical ais ' of. ' cm (Doc ) ) Redraw, on a graph paper, the above figure (Doc ). 2) The straight line passing through and ' meets the optical ais ' at a point. 2-) Eplain why the point is the optical center of. 2-2) Represent the lens on the figure. ) To determine the focal length of the lens, we draw a luminous ray issued from parallel to the optical ais. -) Complete the path of this ray. -2) Indicate on the figure, with justification, the position of the image focus F' of. -) Deduce the focal length of. Eercise 2 (4 points) Pressure of a confined gas The aim of this eercise is to determine the pressure of a confined gas. For this purpose, we performed the eperiment represented by the adjacent document (Doc 2) and obtained: H = 7 and h = 50 cm. oth tubes and the tank contain mercury of density ρ = 600 kg/m.take: g = 0 N/kg. ) The pressures at points and are equal. Justify. 2) Calculate the pressure at. ) Deduce the pressure of the confined gas. /2 Vacuum H (Doc 2) Confined gas h

2 Eercise (6 points) lternating voltage and the adjustment of an oscilloscope The adjacent document (Doc ) represents the waveform of an alternating voltage u delivered, across its terminals, by a low frequency generator (LFG). The maimum value of the voltage u is = 5 V and its period is T = 20 ms. ) djustment of the oscilloscope. -) Determine the vertical sensitivity Sv of the oscilloscope. -2) Determine the horizontal sensitivity Sh of the oscilloscope. 2) Voltage u. 2-) Indicate the type of the alternating voltage u. 2-2) Calculate the frequency of u. (Doc ) 2-) Calculate the effective value of u. 2-4) lamp, of rated voltage 5 V, is directly connected across the terminals of the (LFG). Specify if the lamp glows strongly, normally or dimly. Eercise 4 (4 points) Determination of the density of a liquid The aim of this eercise is to measure the density of a liquid. For this purpose, we have a solid (S) whose weight is of magnitude W = 5 N, a spring balance and a graduated cylinder containing liquid of volume V = 250 ml as shown in the adjacent document (Doc 4). We suspend (S) from the spring balance and immerse it completely in liquid. t equilibrium, the level of the liquid corresponds to the graduation V2 = 00 ml and the spring balance indicates 4.6 N as shown in the adjacent document (Doc 5). Take: g = 0 N/kg. The solid (S) is subjected to the rchimedes upthrust F of magnitude F. ) Indicate the line of action and the direction of F. 2) Let W app be the apparent weight of (S), of magnitude Wapp. Write the epression of F in terms of W and Wapp. ) Calculate F. 4) Calculate, in ml, then convert to m, the volume V of the displaced liquid. 5) Determine the density of the liquid in kg/m. 2/2

3 الهيئة األكاديمي ة المشتركة قسم: العلوم المادة: الفيزياء الشهادة: المتوسطة نموذج رقم 4 المد ة: ساعة واحدة أسس التصحيح )تراعي تعليق الدروس والتوصيف المعد ل للعام الدراسي وحتى صدور المناهج المطو رة( Eercise (5 points) Determination of the focal length of a converging lens Question nswer Mark ' cm 2- luminous ray, issued from and passing through the optical center of a converging lens, emerges without deviation and passes through the real image of. The points, and the optical center of the lens are thus aligned. In addition, the optical center belongs to the optical ais. Then the optical center is the intersection between the ray and the optical ais. In our case, it is the point. 2-2 ' cm /

4 - ' cm -2 When a ray of light falls parallel to the optical ais of a converging lens, the emerging ray passes through the image focus F. Hence, F is the intersection between this emergent ray and the optical ais. ' F cm - f = F. f = 4 5 = 20 cm. Eercise 2 (4 points) Pressure of a confined gas Question nswer Mark and are in the same liquid at equilibrium and in the same horizontal plane. 2 P = ρ g H + PVacuum P = = Pa. P = ρ g h + PGas PGas = P ρ g h = P ρ g h PGas = = 4000 Pa 2/

5 Eercise (6 points) lternating voltage and the adjustment of an oscilloscope Question nswer Mark - The voltage u has a maimum value covering Ym = div. SvYm Sv Ym 5 S v 5 V / div -2 The voltage u has a period T covering X = 0 div. T ShX T S h X 20 S h 2 ms / div 0 2- lternating sinusoidal voltage. 2-2 f T with T = 20 ms = s f 50 Hz U 2 5 U 0.6 V The lamp glows dimly because it is connected across an alternating voltage of effective value that is less than its rated voltage (0.6 V < 5 V). Eercise 4 (4 points) Determination of the density of a liquid Question nswer Mark The line of action of F is vertical and its direction is upward. 2 F = W Wapp F = = 0.4 N. 4 V = V2 V = = 50 ml V = l = m or m 5 F = Vimmersed g but Vimmersed = V because (S) is completely immersed in the liquid therefore F = ρ V g F V g kg / m /

قسم: العلوم. This test includes three mandatory exercises. The use of non-programmable calculators is allowed.

قسم: العلوم. This test includes three mandatory exercises. The use of non-programmable calculators is allowed. الهيئة األكاديمي ة المشتركة قسم: العلوم نموذج مسابقة )يراعي تعليق الدروس والتوصيف المعد ل للعام الدراسي 017-016 المادة: الفيزياء الشهادة: الثانوية العام ة الفرع: علوم الحياة نموذج رقم 1 المد ة: ساعتان