**Question 1 is Compulsory**

**Answer any 4 Question From Question 2 to Question 7**

**Answer Any 3 Question From Question 8 to Question 11**

**Answer Any 3 Question From Question 12 to Question 15**

A short electric dipole (which consists of two point charges, +q and -q) is placed at the centre 0 and inside a large cube (ABCDEFGH) of length L, as shown in Figure 1. The electric flux, emanating through the cube is:

a) `q"/"4piin_9L`

b) zero

c) `q"/"2piin_0L`

d) `q"/"3piin_0L`

Concept: Electric Dipole

The equivalent resistance between points. a and f of the network shown in Figure 2 is :

a) 24 Ω

b) 110 Ω

c) 140 Ω

d) 200 Ω

Concept: Cells, Emf, Internal Resistance

A moving electron enters ·a uniform and perpendicular magnetic field. Inside thema~netic field, the electron travels along:

a) a straight line.

b) a parabola

c) a circle

d) a hyperbola

Concept: Magnetic Field Intensity Due to a Magnetic Dipole (Bar Magnet) Perpendicular to Its Axis

A fish which is at a depth of l2 em .in water `(mu = 4/3)` is viewed by an observer on the bank of a lake. Its apparent depth as observed: by the observer is:

a) 3 cm

b) 9 cm

c) 12 cm

d) 16 cm

Concept: Refraction

if `E_p` and `E_k` represent potential energy and kinetic energy respectively, of an orbital electron, then, according to B9hr's theory:

a)`E_k = -E_p"/"2`

b) `E_k = -E_p`

c) `E_k = -2E_p`

d) `E_k = 2E_p`

Concept: Bohr'S Model for Hydrogen Atom

What is meant by the term Quantization of charge?

Concept: Quantisation of Charge

A resistor R is connected to a cell of-emf e and internal resistance r. The potential difference across the resistor R is found to be V. State the relation between e, V, Rand r.

Concept: Cells, Emf, Internal Resistance

Three identical cells each of emf 2V and internal resistance 10 Ω are connected in series to form a battery. The battery is then connected to a parallel combination of two identical resistors, each of resistance 6 Ω. Find the current delivered by the battery.

Concept: Combination of Resistors – Series and Parallel

State how magnetic susceptibility is different for the three types of magnetic materials, i.e. diamagnetic, paramagnetic and ferromagnetic materials

Concept: Permanent Magnets and Electromagnets

An emf of 2V is induced in a coil when the current in it is changed from 0A to 10A in 0·40 sec. Find the coefficient of self-inductance of the coil.

Concept: Electromagnetic Induction

How are electric vector ` (vec E)`, magnetic vector (`vec B)` and velo~ity vector `(vec c)` oriented in an electromagnetic wave?

Concept: Electromagnetic Waves

State any two methods by which ordinary light can be polarised

Concept: Polarisation

A monochromatic ray of light falls on a regular prism. What is the relation between the angle of incidence and angle of emergence in the case of minimum deviation?

Concept: Refraction of Monochromatic Light

What type of lens is used to correct long-sightedness?

Concept: Lenses

Write two important advantages of reflecting telescope over a refracting telescope.

Concept: Optical Instruments - Telescope

Wavelengths of the first lines of the Lyman series, Paschen series and Balmer series, in hydrogen spectrum are denoted by `lambda_L, lambda_P and lambda_B` respectively. Arrange these wavelengths in increasing order.

Concept: Energy Levels

What is the significance of binding energy per nucleon of a nucleus of a radioactive element?

Concept: Mass-energy and Nuclear Binding Energy - Nuclear Binding Energy

Write one balanced equation to show Nuclear fission

Concept: Nuclear Energy - Nuclear Fusion – Energy Generation in Stars

Whatis the difference between analogue signal and. digital signal?

Concept: Bandwidth of Signals

Derive an expression for the intensity of electric field at a point in broadside position or on [4)

an equatorial line of an electric dipole.

Concept: Electric Dipole

Two point charges of 10C each are kept at a distance of 3m in the vacuum. Calculate their electrostatic potential energy.

Concept: Electrical Potential Energy of a System of Two Point Charges and of Electric Dipole in an Electrostatic Field

Four capacitors, C_{1}, C_{2}, C_{3} andC_{4} are connected as shown in Figure 3 below. Calculate equivalent capacitance of the circuit between points X . and Y.

Concept: Capacitance of a Parallel Plate Capacitor with and Without Dielectric Medium Between the Plates

Draw labelled graphs to show how electrical resistance varies with temperature for:

1) a metallic wire.

2) a piece of carbon

Concept: Temperature Dependence of Resistance

Two resistors R1 = 400Ω and R_{2} = 20 n are connected in parallel to a battery. If heating the power developed in R_{1} is 25 W. find the heating power developed in R_{2}

Concept: Combination of Resistors – Series and Parallel

With the help of a labelled diagram, show that the balancing condition of a Wheatstone bridge is

`R_1/R_2 = R_3/R_4` where the terms have their usual meaning.

Concept: Wheatstone Bridge

An I0m long uniform metallic wire having a resistance of 20Ω IS used as a potentiometer wire. This wire is connected in series with another resistance of 480Ω

and a battery of emf 5V having negligible internal resistance. If an unknown emf e is balanced across 6m of the potentiometer wire, calculate

1) the potential gradient across the potentiometer wire

2) the value of the unknown emf e.

Concept: Metre Bridge

Explain the term hysteresis

Concept: Magnetic Force

Name three elements of the earth's magnetic field which help in defining earth's magnetic field completely.

Concept: The Earth’S Magnetism

Obtain an expression for magnetic flux density B at the centre of a circular coil of radius R, having N turns and carrying a current I

Concept: Magnetic Force

A coil of self-inductance 2.5H and resistance 20Ω is connected to a battery of emf 120V having the internal resistance of 5 n. Find:

1) The time constant of the circuit.

2) The current in the circuit in steady state

Concept: Inductance - Mutual Inductance

Figure 4 below shows a capacitor C, an inductor L and a resistor R, connected in series

to an a.c. supply of 220 V

Calculate:

1) The resonant frequency of the given CLR circuit.

2) Current flowing through·the circuit.

3) Average power consumed by the circuit.

Concept: Combination of Capacitors

In a series LCR circuit, what is the phase difference between V_{L} and V_{C} where V_{L} is the potential difference across the inductor and V c is the potential difference across the capacitor?

Concept: Potential Difference and Emf of a Cell

On the basis of Huygens Wave theory of light, show that angle of reflection is equal to the angle of incidence. You must draw a labelled diagram for this derivation

Concept: Proof of Laws of Reflection and Refraction Using Huygen'S Principle

State any one difference between interference of light and diffraction of light

Concept: Interference

Laser light of wavelength 630 nm is incident on a pair of slits which are separated by 1.8 mm. If the screen is kept 80 cm away from the two slits, calculate:

1) fringe separation i.e. fringe width.

2) distance of 10^{th} bright fringe from the centre of the interference pattern

Concept: Interference

Show graphically the intensity distribution in Fraunhofer's single slit diffraction experiment. Label the axes.

Concept: Fraunhofer Diffraction Due to a Single Slit

A point object O is placed at a distance of 15cm from a convex lens L of focal length 1 Ocm as shown in Figure 5 below. On the other side of the lens, a convex mirror M is placed such that its distance from the lens is equal to the focal length of the lens. The final image formed by this combination is observed to coincide with the object O. Find the focal length of the convex mirror

Concept: Ray Optics - Mirror Formula

What is the chromatic aberration? How can it be minimised or eliminated?

Concept: Lenses

Draw a labelled ray diagram showing the formation of a final image by a compound microscope at least distance of distinct vision

Concept: Optical Instruments - The Microscope

With regard to an astronomical telescope of refracting type~ state how you will increase its:

1) magnifying power

2) resolving power

Concept: Optical Instruments - Telescope

In an experiment of the photoelectric effect, the graph of maximum kinetic energy E_{K} of the emitted photoelectrons versus the frequency v of the incident light is a straight line AB shown in Figure 6 below:

Find:

1) Threshold frequency of the metal

2) The work function of the metal.

3) Stopping potential for the photoelectrons emitted by the light of frequency `v = 30 xx 10^14 Hz`

Concept: Photoelectric Effect - Hertz’S Observations

State how de-Broglie wavelength (`lambda`) of moving particles varies with their linear momentum (p).

Concept: de-Broglie Relation

State any one phenomenon in which moving particles exhibit wave nature.

Concept: Wave Nature of Matter

On the basis of Bohr's theory, derive an expression for the radius of the n^{th} orbit of an electron of the hydrogen atom.

Concept: Bohr'S Model for Hydrogen Atom

Using the constants given on page 8 ofthis·Paper, find the minimum wavelength of the emitted X rays, when an X-ray tube is operated at 50 kV.

Concept: Continuous and Characteristics X-rays

Define half-life of a radioactive substance

Concept: Mass-energy and Nuclear Binding Energy - Nuclear Binding Energy

Using the equation `N = N_0e^(-lambdat)` obtain the relation between half-life (T) and decay constant (`lambda`) of a radioactive substance.

Concept: Radioactivity - Law of Radioactive Decay

With the help of a suitable example and an equation, explain the term pair production.

Concept: Atomic Masses and Composition of Nucleus

Draw a labelled diagram of a full wave rectifier. Show how output voltage varies with time if the input voltage is a sinusoidal voltage.

Concept: Semiconductor Diode

Give the truth table and circuit symbol for NAND gate

Concept: Digital Electronics and Logic Gates