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Q.1 Name the mode of propagation of radio waves which travel in straight line from transmitting antenna to the receiving antenna? Q.2 What is the meaning of term attenuation in the communication system? Q.13 Draw symbol and reverse bias V-I characteristics of zener diode. Explain briefly, which property of the characteristics enables us to use zener diode as voltage regulator. Q.14 The energy of electron in the hydrogen orbit is given by -13.6/n2 in eV. Use this expression to show that the hydrogen atom can’t have energy of -6.8eV. [b] Spacing between the lines within given set f observed hydrogen spectrum decreases as ‘n’ increases. Q.3 A parallel beam of monochromatic light falls normally on a single narrow slit. How does angular width of the central maximum in the resulting diffraction pattern depend on the wavelength of the light used? Q.4 Assuming the nuclei to be spherical in shape, how does the surface area of nucleus of mass number A1, compare with that of nucleus of mass number A2? Q.15 Find out the expression for the magnetic field at a point on the central axis of the solenoid carrying current I and having number of turns per unit length n’. Q.5 Out of the two characteristics the mass number and the atomic number of a nucleus, which does not change during beta decay? Q.16 Modern telescopes prefer using suitable mirrors over using suitable lenses. Give two reasons for this preference. Q.6 A physical quantity associated with electrical conductivity has unit ohm-meter. Identify this physical quantity. Q.17 Q.7 The frequency of oscillation of the electric field vector of certain em wave has frequency 5 x 1014Hz. What is the frequency of oscillation of corresponding magnetic field vector and to which part of em spectrum does it belong? Why is it necessary to slow down the neutrons, produced through the fission of U235 nuclei, to sustain the chain reaction? What type of nuclei are needed for slowing down of the neutrons? Q.18 An ac voltage is applied across an LCR circuit. Draw the phasor diagram for this circuit when [a] capacitive reactance exceeds the inductive reactance [b] when inductive reactance exceeds the capacitive reactance. Use E=E0 sing ωt Q.19 Define coefficient of mutual induction and write its SI unit. Obtain the mutual inductance of a pair of circular coils of radius r1 and r2 and r1<<r2. The coils have been placed coaxially with their centers coinciding. Q.20 The amplitude modulated carrier wave of angular frequency ωc, contains frequency ωc, ωc+ωm, ωcωm where ωm is the frequency of modulating signal. Discuss in brief with the help of block diagram, the essential details of simple method used for detecting the modulating signal for this modulated carrier wave. Q.21 Name and define the two elements of the earth’s magnetic field other than the horizontal component of earth’s magnetic field. Why do we say that at places like delhi and Mumbai, a magnetic needle shows true north direction accurately as compared to other places in india. Q.22 A long straight wire of cross section, of radius ‘a’ carries steady current I. The current is uniformly distributed across the cross section of the wire. Use Ampere’s circuital law to show that the Q.8 Q.9 Q.10 A [a] series [b] parallel combination of two given resistors is connected, one by one, across a cell. In which case will the terminal potential difference across the cell have higher value? Write Einstein’s photoelectric equation in terms of the stopping potential and the threshold frequency for a given photosensitive material. Draw a plot showing variation of stopping potential vs frequency of the incident radiation. An em wave is travelling in a medium with velocity v=v i. The electric field oscillations, of this em wave are along y axis [a] identify the direction in which oscillations of magnetic field vector takes place. [b] How are the magnitudes of electric and magnetic field in em wave related to each other. Q.11 For what KE of proton, will its associated deBroglie wavelength by 16.5nm? Q.12 Define the dipole moment of electric dipole. How does electric potential due to dipole vary on the dipole axis as function of r, distance of field point from the center of the dipole at large distances? magnetic field, due to this wire, in the region inside the wire, increases in direct proportion to the distance of the field from point on the axis of the wire. Write the value of this magnetic field on the surface of the wire. Q.23 Q.24 In YDS experiment, the two slits are kept 2mm apart and the screen is positioned 140cm away from the plane of the slits. The slits are illuminated with light of wavelength600nm. Find the distance of the third bright fringe, from the central maximum, in the interference pattern obtained on the screen. If the wavelength of incident light were changed to 480nm, find out the shift in the position of third bright fringe from the central maximum. The two plates of a parallel capacitor are 5mm apart. A slab of dielectric, of thickness 4mm is introduced between the plates with its faces parallel to them. The distance between the plates is adjusted so that the capacitance of the capacitor becomes equal to its original value. If the new distance between the plates is equal to 8mm, what is the dielectric constant of the dielectric used? Q.25 A series LCR circuit R=200Ω, L= 4/π H, C=50/π μF. This series combination is connected across an ac source of 220V, 50Hz. Calculate the [a] the impedance of the circuit [b the peak value of the current flowing in the circuit. Calculate the power factor of this circuit and compare this value with one at its resonant frequency. Q.26 [a] Two point charges q1, q2 initially at infinity, are brought one by one to points P1 and P2, specified by position vectors r1 and r2 relative to some origin. What is the potential energy of this configuration? [b] Define an equipotential surface, Draw schematically the equipotential surfaces corresponding to field that uniformly increases in magnitude but remains constant in direction. Q.27 Q.28 What are coherent sources of light? In YDS experiment, two slits are separated by 3mm distance and illuminated by light of wavelength 480nm. The screen is at distance of 2m from the plane of the slit. Calculate the separation between the 8th fringe and 3rd dark fringe observed with respect to the central fringe. The same input signal is applied to both the [input] terminals of given logic gate. If the output is the [a] same as the common input signal[b] inverted with respect to the [common] input signal, identify the logic gate involved in each case. [2] Write the truth tables for each tables for each of the combination shown below. Also identify the logic operations performed by them Q.29 State the two rules that serve as general rules for analysis of electrical circuit. Use these rules to write the three equations that may be used to obtain the values of the three unknown currents in the branches of the circuit given below [a] State the working principle of a potentiometer with the help of circuit diagram [b] Two cells of emf E1 and E2 and internal resistance r1 and r2 are connected in parallel with each other. Obtain expressions for the equivalent emf and equivalent internal resistance of this parallel combination. Q.30 Draw the ray diagram showing the passage of light through a glass prism. Hence obtain a relation between the angles of deviation, incidence and emergence and angle of prism. [b] Show that no ray can pass through the prism whose refracting angle A is greater than twice the critical angle for the material of the prism.