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This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Draw the V-I characterisitics of p-n junction diode in forward bias and in reverse bias. |
Answer» Solution :In a p-n junction , forward biasing is applied by connecting +ve of the battery to p-section and -ve of the battery of n-section. In the CASE of REVERSE biasing, +ve of the battery is connected to n-section and -ve of the battery is connected to p-section . As a result, the strength of the current CARRIERS moving in the circuit will  change. It can be used by taking the arrangement to use it as half or full wave rectifier or in any other form. A graph between voltage and current for forward bias and reverse bias is as shown in the fig. From the fig., we find that during forward bias, the p-n junction offers less resistanceand during reverse bias it offers LARGE resistance. |
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| 2. |
Assertion: Electron moving perpendicular to vecB will perform circular motion. Reason: Force by magnetic field is perpendicular to velocity. |
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Answer» If both ASSERTION and reason are true and reason is the CORRECT explanation of assertion. |
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| 3. |
White light is used to illuminate the two slits in Young's double slit experiment, separation between the slits is b and the screen is at a distance d ( gt gt b) from the slits.At a point on the screen, directly in front of the slits, certain wavelength |
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Answer» `(B^(2))/(d), (b^(2))/(3D)` |
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| 4. |
A current carrying coil is placed with its plane in the magnetic meridian of the earth. When seen from east the current flowing in it appears clockwise. The magnetic. field at its centre is directed towards |
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Answer» North |
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| 5. |
Truth table for the given circuit is |
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Answer»
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| 6. |
Half life of radium is 1600 years. Its average life is : |
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Answer» 3200 years |
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| 7. |
Through a coil of resistance R charge is flowing in such a manner that in every time interval t_(0) the amount of charge flow is reduced by a factor of 1//2. If a total of q charge flows through the coil in very long time, then the total amount of heat generated in the coil will be |
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Answer» `(1)/(4t_(0))q^(2)Rlog_(e)2` |
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| 8. |
Electromagnetic Damping |
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Answer» Solution :Take two hollow thin cylindrical pipes of equal internal diameters made of aluminium and PVC respectively. Fix them vertically with clamps on retort stands. Take a small cylindrical MAGNET having diameter slightly smaller than the inner diameter of the pipes and drop it through each pipe in such a way that the magnet does not touch the sides of the pipes during its fall. You will observe that the magnet dropped through the PVC pipe takes the same time to COME out of the pipe as it would take when dropped through the same height without the pipe. Note the time it takes to come out of the pipe in each case. You will see that the magnet takes much longer time in the case of aluminium pipe. It is due to the EDDY currents that are generated in the aluminium pipe which oppose the change in magnetic FLUX. i.e., the motion of the magnet. The RETARDING force due to the eddy currents inhibits the motion of the magnet. Such phenomena are referred to as electromagnetic damping. Note that eddy currents are not generated in PVC pipe as its material is an insulator whereas aluminium is a conductor. |
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| 9. |
How many alpha and beta -particles are emitted whenU^(238) changes to Pb^(206) due to radioactivity? Atomic number of U^(238) changes to Pb^(206) are 92 and 82 respectively. |
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Answer» Solution :Let, x = number of `ALPHA`-particles emitted `""`y = number of `beta`-particles emitted DECREASE in MASS number = 4x Decrease in atomic number = (2x -y) Here, 4x = 238 - 206 = 32or, x = 8 And, 2x - y = 92 - 82 = 10 or,y = 2x -10 = 2 `xx` 8 - 10 = 6 |
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| 10. |
A 10 kg metal block is attached to a spring of springconstant 1000 N m^(-1). A block is displaced from equilibrium position by 10 cm and released. The maximum acceleration of the block is |
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Answer» 10 `ms^(-2)` `:.` Magnitude of restoring force `F=kx=1000xx0.1=100N` ACCELERATION `a=F/m=(100)/(10)` `:.a=10 m//s^2` |
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| 11. |
Two identical bars, one of paramagnetic material and other of diamagnetic material are kept in a uniform external magnetic field parallel to it. Draw diagrammatically the modifications in the magnetic field pattern in each case. |
Answer» SOLUTION :In PARAMAGNETIC SUBSTANCE more FIELD lines pass on placing the substance in a magnetic field because RELATIVE permeability `mu_(r)` of it is greater than 1 and the substance experiences a feeble force of attraction.  In diamagnetic substance lesser number of field lines pass through the substance when placed in a magnetic field because for it `mu_(r) lt 1` and the substance experiences a feeble force of repulsion. |
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| 12. |
The velocity of light in glass is 2 xx 10^8m//s. If the R.I. of glass w.r.t. water is 9\8, then the velocity of light in water will be : |
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Answer» `1.25 XX 10^8m//s` |
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| 13. |
Light of wavelength 488 nm is produced by an argon laser which is used in the photoelectric effect. When light from this spectral line is incident on the emitter, the stopping (cut-off) potential of photoelectrons is 0.38 V. Find the work function of the material from which the emitter is made. |
| Answer» SOLUTION :`2.16eV=3.46xx10^(-19)J` | |
| 14. |
A point is located at a distance 100 cm from the screen. A lens of focal length 23 cm mounted on a movable frictionless stand is kept between the object and screen. The stand is attached to massless spring of natural length 50 cm and spring constant 800(N)/(m) as shown in the figure. Mass of the stand with lens is 2 kg. Initially spring is in its natural length. Now a sharp impulse J is given to the stand. Answer the following questions. Q. Choose the correct options (s): |
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Answer» Impulse J imparted to the stand is `8kg(m)/(sec)`  `f=+23cm` `(1)/(100-x)+(1)/(x)=(1)/(23)` `implies(100)/(100x-x^(2))=(1)/(23)` `x^(2)-100x+2300=0` `x=(100+-sqrt(10000-9200))/(2)=50+-10sqrt(2)` `x=(50-10sqrt(2))cm,(50+10sqrt(2))cm`. Mean position is `x=50` REAL images will be formed when x `=(50-10sqrt(2))cm` or `x=(50+10sqrt(2))cm`. since time difference between two consecutive real image formation on SCREEN in same and this repeats four times in an oscillation, so displacement from mean position i.e., `Deltax=10sqrt(2)=(A)/(sqrt(2))`. Here A is amplitude  `impliesA=20cm` `t_(0)=((pi)/(2))/(omega)=(pi)/(2omega)` `omega=sqrt((k)/(m))=sqrt((800)/(2))=20` `t_(0)=(pi)/(40)sec` Impulse imparted `=J=momegaA` `=2.20(1)/(5)=8N-S` |
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| 15. |
A resistance of 600 Omega an inductor of 0.4 H and a capacitor of 0.01 muFare connected in series to an AC source of variable frequency . Find the frequency of AC source for which current in the circuit is maximum. Also calculate the bandwidth and quality factor for the circuit . |
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Answer» Solution :The current in the circuit is maximum at resonant frequency. At resonant` X_(L) = X_(C) ` `omega_(r)L = (1)/(omega_(r)C)omega_(r) = (1)/(sqrt(LC))` `omega_(r) = (1)/(sqrt(0.4 xx 0.01 xx 10^(-6)))` ` = 1.6 xx 10^(4)` Hz Quality FACTOR `Q = (1)/(R) sqrt((L)/(C)) = (1)/(600) sqrt((0.4)/(0.01 xx 10^(-6)))` ` = 0.01 xx 10^(3)` As `Q = ("Resonant frequency ")/("Bandwidth")` `THEREFORE "Bandwidth " = ("Resonant FREQUNCY" )/(Q ) ` = ` (16 xx 10^(3))/(0.01 xx 10^(3))` = 1600 Hz |
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| 16. |
What are standing waves ? Explain how standing waves may be formed in a stretched string. |
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Answer» Solution :Standing waves or STATIONARY `:` When two IDENTICAL progressive ( Transverse or longitudinal ) WAVE travelling opposite directions in a medium ALONG the same straight line , which are superimposed then the resultant wave is called standing wave. Formation ofstanding wave in a stretched string`:` (1) If a string of length 'l' is stretched between two fixed points and set into vibration, a transverse progressive wave begins to travel along the string. (2) The wave isget reflected at the other fixed end. (3) The incident and reflected waves interfere and produce a stationarywave. (4) The stationary wave with nodes and antinodes is shown below. 
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| 17. |
Three capacitors connected in series have an effective capacitance of 4 muF. If one of the capacitance is removed, the net capacitance of the capacitor increases to 6 muF. The removed capacitor has a capacitance |
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Answer» a. `2MUF` |
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| 18. |
Two parallel conductors are separated by 5cm. They carry 6A and 2A in the same direction. Between them the location from first at which magnetic medle lies along B_(H) is |
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Answer» `1.25cm` |
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| 19. |
The figure shows three identical parallel conducting plates X, Y and Z. The separation between X and Y is 2d, and that between Y and Z is d. The six surfaces of the three plates are labeled a,b,c,d,e and f, as shown. The key K_(1) can connect X to ground,and the key K_(2) can connet Z to ground. Initially, both keys are open. Y has Q charge, X and Z have no charge. If K_(2) is closed and K_(1) remains open, the charges on the surfaces a,b,c,d,e and f will be respectivel y |
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Answer» `0,0,0,Q,-Q` and `0` |
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| 20. |
In an experiment with potentiometer to measure the internal resistance of a cell, when the cell is shunted by 5Omega, the null point is obtained at 2m. when cell is shunted by 20Omega the null point is obtained at 3m. The internal resistance of cell is |
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Answer» `2OMEGA` |
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| 21. |
Two equal insulating threads are placed parallel to each other. Separation between the threads (= d) is much smaller than their length. Both the threads have equal and opposite linear charge density on them. The electric field at a point P, equidistant from the threads (in the plane of the threads) and located well within (see figure) is E_0. Calculate the field at mid point (M) of line AB. |
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Answer» |
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| 22. |
The figure shows three identical parallel conducting plates X, Y and Z. The separation between X and Y is 2d, and that between Y and Z is d. The six surfaces of the three plates are labeled a,b,c,d,e and f, as shown. The key K_(1) can connect X to ground,and the key K_(2) can connet Z to ground. Initially, both keys are open. Y has Q charge, X and Z have no charge. If K_(1) is closed and K_(2) remains open, the charges on the surfaces a,b,c,d,e and f will be respectively. |
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Answer» `0, -Q,Q,0,0` and `0` |
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| 23. |
Hydrogen atoms in very high quantum state have been observed in radio astronomy. The wavelength of radiation emitted when hydrogen atom makes transition from n = 110 state to n = 109 state is lambda = 5.8 cm. Imagine a He atom in which one of the electrons has been excited to n = 110 state. What will be wavelength of emitted radiation if the electron makes transition to n = 109? |
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Answer» |
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| 24. |
The figure shows three identical parallel conducting plates X, Y and Z. The separation between X and Y is 2d, and that between Y and Z is d. The six surfaces of the three plates are labeled a,b,c,d,e and f, as shown. The key K_(1) can connect X to ground,and the key K_(2) can connet Z to ground. Initially, both keys are open. Y has Q charge, X and Z have no charge. If both K_(1) and K_(2) are closed, the charges on the surfaces a,b,c,d,e and f will be respectively |
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Answer» `0,Q,-Q,0,0` and `0` |
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| 25. |
Minimum work done to shift a body of mass m from a circular orbit of 2R to a higher orbit of radius 3R around the earth (R = Radius of earth): |
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Answer» `(GM m)/(12R)` `=(-GMm)/(3R)+(GMm)/(2R)=(GMm)/(6R)` Thus correct choice is (B). |
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| 26. |
A flexible wire of irregular shape, abcd, as shown in the figure, turns into a circular shape when placed in a region of magnetic field which is directed normal to the plane of the loop away from the reader. Predict the direction of the induced current in the wire. |
| Answer» SOLUTION :Anticlockwise/adcba. | |
| 27. |
A moving coil D' Arsonval galvanometer is based on the |
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Answer» heating EFFECT of current |
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| 28. |
A moving positron and electron both with kinetic energy 1 Me V annihilate with each other and emits two gamma photons. If the rest mass energy of an electron is 0.51 MeV, the wavelength of each photon is ? |
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Answer» `5.1xx10^(-3)Å` |
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| 29. |
NAND and NOR gates are called universal gates primarily, because they |
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Answer» are available universally |
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| 30. |
A particle having charge q moves with a velocity v through a region in which both an electric field vecE and a magnetic field B are present. The force on the particle is |
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Answer» `qvecE+q(vecBxxvecv)` |
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| 31. |
A body falls from rest. In the last second of its fall, it covers half of the total distance then the total time of its fall is |
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Answer» `(2-sqrt(2))s` s/2 =0 +g/2(2n-1) s=g(2n-1)=9.8(2n-1) Also `s=0+(1)/(2)gn^(2)=4.9n^(2)` `:. 9.8(2n-1)=4.9n^(2)` or `n^2 -4n+2=0` Solving the quadrtic EQUATION, `n=(2+sqrt(2))` second. |
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| 33. |
196 के अभाज्य गुणनखण्डों की घातों का योगफल है : |
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Answer» 1 |
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| 34. |
(a) In an RLC circuit, can the amplitude of the voltage across an inductor be greater than the amplitude of the generator emf? (b) Consider an RLC circuit with emf amplitude E_m = 10 V, resistance R = 5.0 Omega, inductance L = 1.0 H, and capacitance C = 1.0 muF. Find the amplitude of the voltage across the inductor at resonance. |
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Answer» |
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| 35. |
The resistance of an Carbon wire is 10 Omega. A current of 30 mA is flowing in it at 20^(0)C. If p.d. across its ends constant then its temperature is increased to 120^(0)C then the current flowing in the wire will be in mA ( alpha_(C)=5 xx 10^(-3)//^(0)C) |
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Answer» 20 |
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| 36. |
Three resistors 2 Omega , 4Omega and 5 Omegaare combined in parallel. What is the total resistance of the combination ? |
| Answer» SOLUTION :(20/19) `OMEGA` | |
| 37. |
The capacitance of a capildtor is 10 muF . The potential difference on it is 50 V. If the distance between its platsis halved, what will he the potential difference now ? |
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Answer» 100 V `:. V = (sigma)/(epsilon_(0)).d `where `(sigma)/(epsilon_(0)) ` is constant `:. V prop d` `:. (V)/(V) = (d)/(d)` `:. (V)/(50)= (d)/(2D) :. V = (50)/(2) = 25 V ` |
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| 38. |
In the foregoing question, the balancing length between the p.d. between the points M and C in cms willbe |
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Answer» 40 |
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| 39. |
Assertion: Magnitude of electric force acting on a proton and an electron, moving in a uniform electric field is same, where as acceleration of electron is 1836 times that of a proton and opposite in direction. Reason:Electron is lighter than proton. |
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Answer» Both ASSERTION and Reason are true and Reason is the correct EXPLANATION of Assertion |
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| 40. |
A, B and C are three points in a uniform electric field. The electric potential is |
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Answer» Maximum at B |
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| 41. |
The equation of a progressive wave is given by y=asin200pi(t-x/300),where x is in meter and t is in seconds. The frequency and velocity of the wave respectively |
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Answer» 330 cycles/sec, 100m/s |
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| 42. |
Select the correct statement about electric charge |
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Answer» CHARGE can be converted into energy and energy can be converted into charge |
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| 43. |
The average energy of molecules in a sample of oxygen gas at 300K are 6.2 J xx 10^(-21) J. The corresponding values at 600K are |
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Answer» `12.12xx10^(-21)J` `(E_(2))/(E_(1))=(T_(2))/(T_(1))=600/300=2` `E_(2)=2E_(1)=2xx3/2KT` `=3xx1.38xx10^(-23)xx300` `=12.42xx10^(-21)J` So CORRECT choice is (d). |
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| 44. |
A hemispherical bowl of radius R=5 metre is fixed on a horizontal surface its inner surface to be smooth. Three smooth and perfectly inelastic ball of mass 3mg, 4kg and 5kg simultaneously released from the edge of bowl in such way that during the collision with each other, their kinetic energy loss is maximum. If the maximum kinetic energy lost during the collision is 300n Joule. Find the value of n. (take g=10 m//s^(2)) |
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Answer» Solution :Make collision in such a wavy that all balls WOULD be stopped at bottom the bowl. So, maximum KINETIC ENERGY LOSS `=(1)/(2)xx(2xx5xx10)(3+4+5)=600J` |
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| 45. |
A solenoid is connected to a battery so that a steady current flows through it. If an iron core is inserted into the solenoid, will the current increase or decrease ? Explain. |
| Answer» Solution :The current flowing through solenoid coil decrease. As the iron core is INSERTED into the solenoid, the magnetic field and consequently the magnetic FLUX increases. In accordance with Lenz.s LAW the INDUCED current resists the increase in magnetic flux. Hence, an induced current is set up in the solenoid coil in a direction opposite to that of battery current. As a result, the current flowing in soil decreases. | |
| 46. |
A small candle 2.5 cm height is placed in front of a concave mirror of radius of curvature 36 cm at a distance 27 cm from the concave mirror. i.At what distance from the mirror should a screen be placed in order to receive a sharp image ? ii. Describe the nature and size of the image. iii.If the candle is moved close to the mirror, what will be the position of the screen ? |
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Answer» Solution :`h_(0) = 2.5 cm, R = 36 cm , f = (R)/(2) = ~ 18` cm , u = - 27 cm i. `(1)/(f) = (1)/(u) + (1)/(v) "" (1)/(v) = (1)/(f) - (1)/(u)""= (1)/(-18) - (1)/(-27)` v = - 54 cm The negative sign indicates that image is formed in front of mirror (on the same side as that of the object ) `therefore` screen should be placed at a distance of 54 cm in front of the mirror . ii.m= `(h_(i))/(h_(0)) = (-v)/(u) "" h_(i) = (-v)/(u) XX h_(0)= (-54)/(27 ) xx 2.5 = - 5 cm ` Image is magnified. Negative sign shows that image is real and inverted . iii.If the candle is moved CLOSER to the mirror, then u decreases and v increases. HENCE screen has to be moved farther and farther. When u `lt` 18 cm, image formed will be virtual and hence can.t be formed on the screen . |
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| 47. |
Site of synthesis of ribosomes. |
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Answer» nucleus |
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| 48. |
The de Broglie wavelength of an electron and the wavelength of a photon are equal and its value is lamda= 10^(-10)m. Which one has a higher kinetic energy? |
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Answer» |
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| 49. |
Discuss the functions of key components in Robots? |
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Answer» Solution :The robotic system mainly consists of sensors, power supplies, CONTROL systems, manipulators and necessary software. Most robots are COMPOSED of 3 main parts: (i) The Controller also known as the "brain" which is run by a computer program. It gives COMMANDS for the moving parts to perform the job. (ii) Mechanical parts motors, pistons, grippers, wheels, and gears that make the ROBOT move, grab, turn, and lift. (iii) Sensors to tell the robot about its surroundings. It helps to determine the sizes and shapes of the objects around, distance between the object, and directions as well. 
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