**Physics**

· Answers to this Paper must be written on the paper provided separately.

· You will not be allowed to write during the first 15 minutes.

· This time is to be spent in reading the Question Paper.

· The time given at the head of this Paper is the time allowed for writing the answers.

**·**

**Section I**

**is compulsory. Attempt any four questions from**

**Section II**

· The intended marks for questions or the parts of questions given in brackets [ ].

**SECTION I (40 Marks)**

**Attempt all questions from this Section**

**Question 1**If ‘m’ is the mass of the body, ‘v’ its velocity and ‘p’ the momentum then write a relationship between change in momentum , mass and velocity of the body when :

(i)

*v*is almost equal to*c*,the velocity of light ;(ii)

*v*is very-very less as compared to*c*,the velocity of light. (2) (b) Diagram alongside shows a weightless lever in equilibrium. Neglect friction at the fulcrum F.

- State the principle of moments as applied to the alongside lever.
- Define mechanical advantage and calculate its value for the given lever.
- Name the type of lever which has mechanical advantage greater than 1.(1+2+1)

(c) When an arrow is shot from a bow, it has kinetic energy in it. Explain briefly from where does it get its kinetic energy?. [2] (d) What energy conversions take place in the following when they are working- (i) Electric toaster (ii) Microphone?. [2]

**Question 2**(a) (i) A monochromatic beam of light of wavelength Î» passes from air into a glass block. Write an expression to show the relation between the speed of light in air and the speed of light in glass. (ii) As the ray of light passes from air to glass, state how the wavelength of light changes. Does it increase, decrease or remain constant? (1+1)

(b) An object is placed in front of a converging lens at a distance greater than twice the focal length of the lens. Draw a ray diagram to show the formation of the image. [2]

(c) Mention one difference between reflection of light from a plane mirror and total internal reflection of light from a prism. [2]

(d) The V-I graph for a series combination and for a parallel combination of two resistors is as shown in the figure below:-

Which of the two, A or B, represents the parallel combination? Give a reason for your answer. [2]

(e) Of the three connecting wires in a household circuit:- [2]

- Which two of the three wires are at the same potential?
- In which of the three wires should the switch be connected?

**Question 3**(a) The diagram given below shows a right-angled prism with a ray of light incident on the side AB. (The critical angle for glass is 42

^{0}) [3]

- Copy the diagram and complete the path of the ray of light in and out of the glass prism.
- What is the value of the angle of deviation shown by the ray?

(b) (i) A particular type of high energy invisible electromagnetic rays help us to study the structure of crystals. Name these rays and give another important use of these rays.

(ii) How does the speed of light in glass change on increasing the wavelength of light? [4]

(c) (i) With the help of a well-labelled diagram show that an apparent depth of an object, such as a coin, in water is less than its real depth.

(ii) How is the refractive index of water related to the real depth and the apparent depth of a column of water? [3]

**Question 4**(a) [1+2]

- State Ohm's law.
- State the factors that alter the resistance af a conductor.

(b) The alongside circuit diagram shows three resistance 2Ω, 4Ω and RΩ connected to a battery of emf 2V and internal resistance 3Ω. A main current of 0.25A flows through the circuit: [5]

- What is the P.D., across the 4Ω RΩ AΩ resistor?
- Calculate the PD., across the internal resistance of the cell.
- What is the PD., across the RΩ or the 29 resistors?
- Calculate the value of R.

(a) State two ways of increasing the speed of rotation of a D.C. motor. [2]

**SECTION II (40 Marks)**Attempt any four questions from this Section

**Question 5**(a) (i) A stone of mass 64.0 g is thrown vertically upward from the ground with an initial speed 20.0 m/s. The gravitational potential energy at the ground level is considered be zero. Apply the principle of conservation energy and calculate the potential energy at the maximum height attained by the stone. (g = 10 m s

^{-2}) . [3] (ii) Using the same principle, state what will be the total energy of the body at its half-way point?

(b) Define 'joule', the SI unit of work and establish relationship between the SI and CGS unit of work . [3]

(c) (i) Draw a labelled diagram of a block and tackle system of pulleys with two pulleys in each block. Indicate the directions of the load, and effort and tension in the string. [4] (ii) Write down the relation between load and the effort of the pulley system.

**Question 6**(a) Explain, why bottled soft drinks are more effectively cooled by cubes of ice than by ice water? [5]

(b)10 g of ice at 0

^{0}C absorbed 5,460 J of heat to melt and change into water at 50^{0}C. Calculate the specific latent heat of fusion of ice. [Specific heat capacity of water is 4,200 J/kg/^{0}C]. [4](c) In an experiment to determine the specific latent heat of vaporisation af steam L, the following measurements were taken. Mass of calorimeter + stirrer = x kg. Mass of water = y kg. Initial temperature of water = t

_{0}1,°C Final temperature of mixture = t_{2}°C [Given : S.H.C., of calorimeter and water are S_{1}and S_{2}respectively]. Express in terms of above data. [4]**Question 7**(a) [6]

- State any two characteristics of a wave motion.
- What is the relation between frequency, wavelength and speed of a wave?
- A longitudinal wave of wavelength l cm travels in air with a speed of 330 m/s. Calculate the frequency of the wave. Can this wave be heard by a normal human being?

(b) Two waves A and B have wavelengths 0·01 Å and 9000 Å respectively. [4]

- Name the two waves.
- Are the speeds of these two waves equal when they travel in vacuum?
- If the amplitude of a wave is doubled what will be the effect on its loudness?

**Question 8**(a) Given alongside is the circuit diagram in which three resistances 1Ω, 2Ω and 3Ω are connected to a cell of emf 2 V and internal resistance 0.5Ω. [6]

- Calculate the total resistance of the circuit.
- What is the reading of the ammeter?
- What will be the ammeter reading if an exactly similar cell is connected in series with the given cell? (b) [4]

- Draw a neat labelled diagram of an a.c.generator.
- What is the magnitude of the emf induced in the coil when its plane becomes parallel to the magnetic held?

**Question 9**(a) The following diagram is the simplified version of an electrode gun which is an integral part of a cathode ray-tube. 'A' is a metal cylinder. [5]

- Copy the diagram in your answer book. Draw a pair of planets P
_{1}and P_{2}to apply electric field, a screen S and an enclosure. - What are the functions of A, B, P
_{1}and P_{2}.

(b) 27 Mg β Al Y 12 --> -->

In the above nuclear reaction. [3]

^{27}Mg_{12}emits α, β-particle and is transformed to aluminium. What is the mass number and the atomic number of aluminium.- Aluminium emits γ ray. What is the resulting nucleus?

(c) [2] 1)Which radiation or particle from radioactivity produces maximum biological damage? 2)State three precautions that must be taken while handling a radio active source.

**Question 10**(a) A block of mass 30 kg is pulled up a slope (diagram alongside) with a constant speed by applying a force of 200 N parallel to the slope. A and B are initial and final positions of the block. [4]

- Calculate the work done by the force in moving the block from A to B.
- Calculate the potential energy by the block.

(b) Diagram alongside gives an arrangement of single moving pulleys. Copy the diagram If the effort applied at the free end of the string is E, [3]

i. Show the direction and magnitude of the forces exerted by the four strings marked (1) to (4).

ii. What is the load which can be lifted by the effort?

iii. Calculate the mechanical advantage of the system of pulleys.

(a) [3] i)State the equation for the relation between the frequency and wave length of light in vacuum. ii)What is the relation between the angle of incidence 'i' in the liquid and the angle of refraction 'r' in the glass?

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