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(i) Draw a neat labelled ray diagram of an astronomical telescope in normal adjustment. Explain briefly its working. (ii) An astronomical telescope uses two lenses of powers 10D and ID. What is its magnifying power in normal

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Explain with the help of a ray diagram, the working of an astronomical telescope. The magnifying power of a telescope in its normal adjustment is 20. If the length of the telescope is 105 cm in this adjustment, find the focal lengths of the two

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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State the importance of coherent sources in the phenomenon of interference. In Young's double slit experiment to produce interference pattern, obtain the conditions for constructive and destructive interference. Hence, deduce the expression for the fringe width. How does the fringe width get affected, if the entire experimental apparatus of YDSE is immersed in

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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What is the de Broglie wavelength associated with an electron, accelerated through a potential differnece of 100

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The work function for the following metals is given: Na: 2.75 eV; K: 2.30 eV; Mo: 4.17 eV; Ni: 5.15 eV. Which of these metals will not give photoelectric emission for a radiation of wavelength 3300 Å from a He-Cd laser placed 1 m away from the photocell? What happens if the laser is brought nearer and placed 50 cm away

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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An oil drop of 12 excess electrons is held stationary under a constant electric field of `2.55×10^4 Vm^(-1)` . If the density of the oil is 1.26 gm/`cm^3` then the radius of the drop is ..........

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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An infinitly long thin straight wire has uniform linear charge density of `1/3` c/m . Then, the magnitude of the electric intiensity at a point 18 cm away is .......... `NC^(–1)`

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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How much positive and negative charge is there in a cup of

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A wire in the form of a tightly wound solenoid is connected to a DC source, and carries a current. If the coil is stretched so that there are gaps between successive elements of the spiral coil, will the current increase or decrease?

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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As the frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the

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220 V,50 Hz, ac is applied to a resistor. The instantancous value of voltage

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A choke coil

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Magnetic flux in a circular coil of resistance `10Omega` changes with time as shown in figure. `ox` direction indicates a direction perpendicular to paper inwards. Column–I Column–II (A) At 1 second induced current is (P) Clockwise (B) At 5 second induced current is (Q) Anticlockwise (C) At 9 second induced current is (R) 0.5 A (D) At 15 second induced current is (S) 5 A (T) None of these

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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In the circuit shown in figure `E=25V, L=2H, C=60 muF, R_1 = 5Omega and R_2=10Omega`. Switch S is closed at `t = 0.` Column-I Column-II (A) Current through `R_1` at t = 0 (P) 0 (B) Current through `R_2` at t = 0 (Q) 5A (C) Current through `R_1` at `t =oo` (R) 2.5 A (D) Current through `R_2` at `t =oo` (S) 7.5 A (T) None of these

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Due to 10 Amp of current flowing in a circular coil of 10 cm radius, the mag. field produced at its centre is `pixx10^(-3)` Tesla. The number of turns in the coil will

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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A beam of protons with a velocity of `4 xx 10^5 m s^(-1)` moves in the direction of uniform magnetic field. It makes an angle of 37° with the magnetic field and follows a helical path. If the time period of helix is `2 xx 10^(-7) s`, then its pitch will

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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Self-Induction Self-induction is the property of a coil by virtue of which the coil opposes any change in the strength of current flowing through it by inducing an emf in itself. This induced emf is also called back emf. When the current in a coil is switched ON, then the self induction opposes the growth of the current and when it is switch OFF, then the self-induction opposes the decay of the current.The inductance that would be needed to store 1 kWh of energy in a coil carrying a 200 A current

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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L-C Oscillations When a capacitor is supplied with an AC circuit, it gets charged.When this charged capacitor is connected with an inductor, current flows through inductor, giving rise to magnetic flux. Hence, induced emf is produced in the circuit. Due to this, the charge on the capacitor decreases and an equivalent amount of energy is stored in the inductor in the form of magnetic Field.In an L-C circuit, angular frequency at resonance is `omega`. What will be the new frequency when inductor’s inductance is made two times and capacitor’s capacitance is made four

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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AC Generator An AC generator produces electrical energy from mechanical work, just the opposite of what a motor does. In it, a shaft is rotated by some mechanical means, such as an engine or a turbine starts working and an emf is induced in the coil.It is based on the phenomenon of electromagnetic induction which states that whenever magnetic flux linked with a conductor (or coil) changes, an emf is induced in the coil. The graph below shows the voltage output plotted against time. Which point on the graph shows that the coil is in a vertical

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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The Transformer Transformer is a device, which is used to increase or decrease the alternating voltage. The transformers are of the following types (i) Step-up transformer (ii) Step-down transformerTransformer is based upon the principle of mutual induction. It consists of two coils, primary coil `(p)` and secondary coil `(s)`, insulated from each other wounded on soft iron core.Often the primary coil is the input coil and secondary coil is the output coil. These soft iron cores are laminated to minimise eddy current loss.Which quantities do not change during transformer

asked Mar 20, 2022 in 12th Physics by varun (6.7k points)

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