Q. A radioactive substance is oxidized. Will there be any change in a nature of its radioactivity ? Give a reason for your answer.

Q. Copy the diagram given below and complete the path of light ray till it emerges out of the prism. The critical angle of glass is ${42}^o$. In your diagram mark the angles wherever necessary.

Q. What do you understand by the term 'Scattering of light'? Which colour of white light is scattered the least and why?

Q. What is meant by noise pollution? Name one source of sound which causes noise pollution.

Q. State the characteristics required in a material to be used as an effective fuse wire.

Q. Some ice is heated at a constant rate, and its temperature is recorded after every few seconds, till steam is formed at ${100}^{o}C$. Draw a temperature time graph to represent the temperature change. Label the two phase changes in your graph.

Q. A stone of mass $m$ is rotated in a circular path with a uniform speed by tying a strong string with the help of your hand. Answer the following questions:
(i) Is the stone moving with a uniform or variable speed?
(ii) Is the stone moving with a uniform acceleration? In which direction does the acceleration act?
(iii) What kind of force acts on the hand and state its direction?

Q. A copper vessel of mass 100g contains 150g of water at ${50}^{o}C$. How much ice is needed to cool it to $5^{o}C$?
Given: Specific heat capacity of copper $=0.4J{g}^{-1}$ ${}^o{C}^{-1}$
Specific heat capacity of water $=4.2J{g}^{-1}$ ${}^o{C}^{-1}$
Specific latent heat of fusion of ice $=336J{g}^{-1}$

Q. An element ${}_z{S}^A$ decays to ${}_{85}{R}^{222}$ after emitting $2\alpha$ particles and $1\beta$ particle. Find the atomic number and atomic mass of the element S.

Q. The V-I graph for a series combination and for a parallel combination of two resistors is shown in the figure. Out of A and B, which one represents the parallel combination? Give a reason for your answer.

Q. A boy uses blue colour of light to find the refractive index of glass. He then repeats the experiment by using red colour of light. Will the refractive index be the same or different in the two cases? Give a reason to support your answer.

Q. (i) Write relationship between the angle of incidence and the angle of refraction for a given pair of media.
(ii) When a ray of light enters from one medium to another having different optical densities it bends. Why does this phenomenon occur?
(iii) Write one condition where it does not bend when entering a medium of different optical density.

Q. (i) What is the principle of method of mixtures?
(ii) What is the other name given to it?
(iii) Name the law on which the principle is based.

Q. Calculate the mass of ice required to lower the temperature of $300g$ of water at $40°C$ to water at $0°C$. (Specific latent heat of ice = 336 J /g, Specific heat capacity of water = 4.2 J/ g°C).

Q. (i) Give an example of a non-contact force which is always of attractive in nature.
(ii) How does the magnitude of this non-contact force on the two bodies depend on the distance of separation between them?

Q. State the characteristics required for a good thermionic emitter.

Q. (i) An effort is applied on the bigger wheel of a gear having 32 teeth. It is used to turn a wheel of 8 teeth. Where is it used?
(ii) A pulley system has three pulleys. A load of 120N is overcome by applying an effort of 50N. Calculate the Mechanical Advantage and Efficiency of this system.

Q. A music system draws a current of $400mA$ when connected to a $12V$ battery.
(i) What is the resistance of the music system?
(ii) The music system is left playing for several hours and finally the battery voltage drops and the music system stops playing when the current drops to $320mA$. At which battery voltage does the music system stop playing?

Q. State two factors upon which the heat absorbed by a body depends.

Q. From the diagram given below, answer the questions that follow :
(i) What kind of pulleys are A and B?
(ii) State the purpose of pulley B.
(iii) What effort has to be applied at C to just raise the load L = 20 kgf?
(Neglect the weight of pulley A and friction).

Q. With reference to the terms Mechanical Advantage, Velocity Ratio and efficiency of a machine, name and define the term that will not change for a machine of a given design.

Q. State the dependence of angle deviation:
(i) On the refractive index of the material of the prism.
(ii) On the wavelength of light.

Q. State two ways by which the frequency of transverse vibrations of a stretched string can be increased.

Q. A lens produces a virtual image between the object and the lens.
(i) Name the lens.
(ii) Draw a ray diagram to show the formation of this image.

Q. What do you understand by the following statements:
(i) The heat capacity of the body is $60J{K}^{-1}$
(ii) The specific heat capacity of lead is $130Jk{g}^{-1}{K}^{-1}$

Q. The ratio of amplitude of two waves is 3:4. What is the ratio of their:
(i) loudness? (ii) frequencies?

Q. Which coil of a step up transformer is made thicker and why ?

Q. (i) Name the waves used for echo depth sounding.
(ii) Give one reason for their use for the above purpose.
(iii) Why are the waves mentioned by you not audible to us?

Q. Calculate the quantity of heat produced in a $20\Omega$ resistor carrying 2.5A current in 5 minutes.

Q. A boy weighing 40kgf climbs up a stair of 30 steps each 20 cm high in 4 minute and a girl weighing 30kgf does the same in 3 minutes. Compare:
(i) The work done by them.
(ii) The power developed by them