new hots class 10

Q 1 .Give two examples of formation of real image from your daily life.

Q 2 .Name the mirror that has virtual focus.

Q 3.Draw a ray diagram to explain sign convention for lenses.

Q4 .Magnification of a mirror is -5.What all information can you infer from this?Draw a posssible ray diagram for the same.

Q 5 .What is meant by power of a lens ?

Q 6.Why do all predaters have their eyes at the front of their head?

Q 7. A then converging lens forms (a)real image (b)virtual image of an object placed in front of it. the size of the image is three times the size of the object in each case.Draw ray diagrams for both the cases.How will the focal lenth of such a lens be affected on cutting it into two halves along the principle axis?

Q 8 .The applied potential difference across a given resister is altered so that the heat produced per second increases by a factor of 16 .By what factor has the applied potential difference changed?

Q 9 . What are magnetic field lines ? Give any two of its properties.

Q 10.A concave lens made of a material of ref. index n1 is kept in a medium of ref.index n2 .A parallel beam of light is incident on the lens.

Complete the path of rays of light

class 10 hots

LIGHT : Reflection and Refraction

Q-1 State one observation from everyday life which tells us that light travels in straight lines.
Q-2 A ray of light is incident on a plane mirror making an angle of 30º with the mirror surface. What will be the angle of reflection?
Q-3 Out of convex mirror and concave mirror, whose focus is situated behind the mirror?
Q-4 Which type of mirror has :
(a) positive focal length?
(b) negative focal length?
Q-5 Which of the two has a greater power : a lens of short focal length or a lens of large focal length?
Q-6 Which type of mirror is used in a solar furnace? Support your answer with reason.
Q-7 Give one example to show that the optical density of a substance is different from its mass density.
Q-8 What is the difference between virtual images produced by concave, plane and convex mirrors?
Q-9 For driving a car what type of mirror would you prefer to see the traffic at your back and why?
Q-10 The mirror outside the driver side of a vehicle is usually a convex mirror. Printed on such a mirror is usually the warning “Vehicles in this mirror are closer than they appear”. What is the reason for this warning?
Q-11 A virtual image cannot be focussed on a screen. Yet when we see a virtual image, we obviously bring it to the screen that is the retina of our eyes. Is this a contradiction?
Q-12 Is it possible for a lens to act as a convergent lens in one medium and a divergent lens in another?
Q-13 Figure below shows a point source of light S, a convex lens L and a plane mirror M. The three are placed such that rays of light from S return to it after reflection from M. (i) What is the distance OS called (ii) To which point (left of S, on S or right of S) will the rays return if M is moved to the left and brought in contact with L?
Q-14 Can a plane mirror be called a spherical mirror?
Q-15 What is the effect on the wavelength of light when it travels from rarer to denser medium?
Q-16 When does Snell’s law fail?

The Human Eye and the Colourful World

Q-1 What happens to the image distance in the eye when we increase the distance of an object from the eye?
Q-2 State one similarity between the human eye and the camera.
Q-3 State one way in which an eye differs from a camera.
Q-4 Some animals have two eyes at the front of their head whereas other animals have two eyes on the opposite sides of their head. Which of them have a wider field of view?
Q-5 What is the colour of sunlight scattered by the dust particles in the atmosphere?
Q-6 State and explain advantages of having two eyes instead of just one.
Q-7 Explain why, if we look at objects through the hot air over a fire, the objects appear to be wavering (moving slightly).
Q-8 Explain why, when the sun is overhead at noon, it appears white.
Q-9 Why do stars seem higher in the sky than they actually are?
Q-10 Why are electric wires usually made of copper and aluminium?
Q-11 Why do electricians wear rubber handgloves while working with electricity?
Q-12 When two resistances of 2each are connected in a certain way, their resultant resistance becomes 1. State whether they are connected in series or parallel combination.
Q-13 Which effect of current is utilised in an electric bulb?
Q-14 State whether an electric heater will consume more electrical energy or less electrical energy per second when the length of its heating element is reduced. Give reason for your answer.
Q-15 Two exactly similar heating resistances are to be used connected across a mains supply to heat some water. Is more heat obtained per minute if they are connected in series or if they are connected in parallel? Give reasons for your answer.
Q-16 A prism causes dispersion of while light while a rectangular glass block does not. Explain.
Q-17 A glass slab is placed over a page on which the word VIBGYOR is printed with each letter in its corresponding colour. (i) Will the image of all the letters be in the same place? (ii) If not, state which letter will be raised to the maximum. Give a reason for your answer.
Q-18 What happens to the lens and the ciliary muscles when you are looking at distant objects?

Electricity

Q-1 Why are electric wires usually made of copper and aluminium?
Q-2 Why do electricians wear rubber handgloves while working with electricity?
Q-3 When two resistances of 2 W each are connected in a certain way, their resultant resistance becomes 1 W . State whether they are connected in series or parallel combination.
Q-4 Which effect of current is utilized in an electric bulb?
Q-5 State whether an electric heater will consume more electrical energy or less electrical energy per second when the length of its heating element is reduced. Give reason for your answer.
Q-6 Two exactly similar heating resistances are to be used connected across a mains supply to heat some water. Is more heat obtained per minute if they are connected in series or if they are connected in parallel? Give reasons for your answer.
Q-7 Two metallic wires A and B of same material are connected in parallel. Wire A has length L and radius r and wire B has length 2L and radius 2r. Compute the ratio of the total resistance of parallel combination and the resistance of wire A.
Q-8 How are materials classified as a conductors or bad conductors of electricity?
Q-9 Why is heat produced when a current is passed through a conductor?
Q-10 Why should the melting point of a fuse wire be low?
Q-11 A bulb gets dimmer for a moment when a geyser, connected across the same source is switched on. Why?
Q-12 A large number of free electrons are present in metals. Why is there no current in the absence of electric potential across it?
Q-13 If a student by mistake connects a voltmeter in series or an ammeter in parallel of a circuit, what will happen?
Q-14 There is an impression among many people that a person touching a high power line gets stuck with the line. Is this true? Explain.

Magnetic Effect Of Electric Current

Q-1 State qualitatively the effect of inserting an iron ‘core’ into a current-carrying solenoid.
Q-2 In household circuits, is a fuse wire connected in series or in parallel?
Q-3 Explain why, a copper wire cannot be used as a fuse wire.
Q-4 Explain why, two magnetic field lines do not intersect each other.
Q-5 Of what substance is the fuse wire made? Why?
Q-6 The following diagram shows two straight wires carrying current. Copy the diagram and draw the pattern of lines of force around them and mark their directions.
Q-7 State the energy change which takes place when a magnet is moved inside a coil having a galvameter at its ends. Name this phenomenon.
Q-8 You have just paid the electricity bill for your house (i) what was it that your family consumed, for which you had to pay?(ii) In what unit was it measured?
Q-9 Make a table with names of 3 electrical appliances used in your home in one column, their power, voltage rating and approximate time for which each is used in one day in the other column.
Q-10 Why do iron filings arrange themselves in a certain pattern around a magnet?
Q-11 Explain why a fuse should be joined with the live wire and not with the neutral wire in a domestic circuit.


Sources of Energy

Q-1 Explain why, many thermal power plants are set up near coal or oil fields.
Q-2 Why are black sufaces used in solar cookers and solar water heaters?
Q-3 Explain how, wind energy comes from the sun in an indirect way.
Q-4 Suggest a safe and efficient method for the disposal of biowastes and sewage materials. How is this method advantageous to us?
Q-5 Explain how, the sun is considered to be the ultimate source of fossil fuels.
Q-6 Why are Biogas plants considered to be boon to the farmers? Give reasons.
Q-7 The waste materials collected from a market complex are scrap paper, thermocol, vegetable waste, tin cans and glass bottles. Which of these can be used for producing biogas? Mention three advantages of converting these into biogas rather than burning them.
Q-8 Why are gaseous fuels preferred to solid fuels in industries?
Q-9 Why CNG is considered an environmental friendly fuel?