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Part 013 – Physics Previous Year Questions

Q1. After long periods of use, a grey spot develops on the inside of a bulb. This is because
(a) the tungsten fi lament evaporates and collects there
(b) the heat of the bulb scorches the glass at the top
(c) dust inside the bulb condenses on the top
(d) glass undergoes a change due to the heat
Ans: (c) At high operating temperatures, tungsten evaporates from the filament and gradually forms a gray film on the inside of the bulb. The inert gas atoms collide with the evaporating tungsten, causing some of the tungsten atoms to return to the filament. Eventually, however, a thin spot develops in the filament. When this happens, the filament will break and the bulb fails.

Q2. Should cars have bumpers that collapse under impact?

(a) Yes, since the offending car should get damaged and pay for the mistake
(b) No, since it would be very expensive to get the car repaired
(c) No, since the colliding car would then ram into the occupants and kill them
(d) Yes, since they help to absorb the impact of a collision and keep the occupants safe
Ans: (d) In automobiles, a bumper is the front-most or rearmost part, ostensibly designed to allow the car to sustain an impact without damage to the vehicle’s safety systems. They are not capable of reducing injury to vehicle occupants in high-speed impacts, but are increasingly being designed to mitigate injury to pedestrians struck by cars.

Q3. Ice cubes are added to a glass of pure water and a glass of pure alcohol. The ice would be

(a) at a higher level in water
(b) at a higher level in alcohol
(c) at the same level in both
(d) floating in alcohol and sinking in water
Ans: (a) Density of water is approx 1g/ml; Density of Ice is approx 0.93g/ml; and Density of 100% pure ethanol is 0.79g/ml. So the density of ice cubes is lesser than water, but higher than alcohol. So it will float in water, but sink in alcohol. This can also be put as: The ice cube will float higher in water as compared to alcohol.

Q4. A person wears spectates with concave lenses. It means that normally (when not using glasses), the image of distant objects is focussed in his eyes

(a) behind the retina
(b) in front of the retina
(c) on the retina
(d) on the blind spot
Ans: (b) A concave lens is used to correct short-sightedness (myopia). In myopia, images are formed in front of the retina, resulting in a blurred image. This occurs when the eye is relatively too long or the refractive powers of the cornea and lens of the eye are relatively too strong.

Q5. What is the principle of a ‘Life Jacket’?

(a) It provides oxygen to a drowning person
(b) It increases the volume of the person to keep him afloat
(c) It decreases the volume of the person to keep him afloat
(d) The person can sit on it like a raft
Ans: (b) The upward-pushing force that keeps things afloat is called buoyancy. For an object to float it must be able to equal its own weight by displacing enough water. A life jacket is mainly filled with gas which has a very low mass. As such when worn by a person, it acts to significantly increase their volume for only a very small increase in their mass. This means that they have a lower density than normal which increases their buoyancy and helps them to float.

Q6. Myopia is the same as

(a) Near sightedness
(b) Astigmatism
(c) Presbyopia
(d) Long sightedness
Ans: (a) Myopia or near-sightedness is condition of the eye where the light that comes in does not directly focus on the retina but in front of it. This causes the image that one sees when looking at a distant object to be out of focus but in focus when looking at a close object. It is corrected by using concave lenses.

Q7. Sun’s heat reaches us by

(a) Conduction
(b) Convection
(c) Radiation
(d) Reflection
Ans: (c) Radiation is a process in which energetic particles or energetic waves travel through vacuum, or through matter-containing media that are not required for their propagation. The sun’s rays reach us in the form of electromagnetic radiation. This type of radiation covers a wide spectrum (that is a wide range of frequencies), but those from the sun are mainly infra-red, visible, and ultra-violet.

Q8. A sphere rolls down on two inclined planes of different angles but same height, it does so

(a) in the same time
(b) with the same speed
(c) in the same time with the same speed
(d) in the same time with the same kinetic energy
Ans: (b) The velocity of the sphere at the bottom depends only on height and acceleration due to gravity. Both these values are constants. Therefore, the velocity at the bottom remains the same whichever inclined plane the sphere is rolled. However, the sphere will take longer time to reach the bottom of the inclined plane having the smaller inclination. The kinetic energy will be the same. What will differ is time taken to reach the bottom.

Q9. In heating frozen foods in sealed pouches in a microwaves, why do you first poke holes in the pouch?

(a) To prevent the steam pressure from bursting open the pouch
(b) To allow the heat to get into the food through the hole
(c) To allow the microwaves to get into the food through the holes
(d) To allow the aroma of the food to come out through the holes
Ans: (a) Anything in a tight skin or shell can explode in a microwave because the water inside can expand and burst through. It is for this very reason that before microwaving, the skin of potatoes should be pricked, winter squash and similar vegetables should be cut in half, eggs should be taken out of shells and holes should be poked in the plastic wrap or sealed pouches of frozen packaged foods.

Q10. A vacuum cleaner works on the principle of pressure difference.
On the moon it will

(a) work as efficiently as on the earth
(b) not work at all
(c) work with reduced efficiency
(d) work with increased efficiency
Ans: (b) Vacuum cleaners work by creating a lower pressure just inside the opening which touches the floor. By creating a low pressure inside the machine, higher air pressure in the room pushes its way into the vacuum cleaner, taking the dirt with it. Because there is no, or very little, atmosphere on the moon, we can’t create a lower or higher gas pressure inside and outside the machine, so dirt cannot be sucked up from the ground. Nothing happens when a vacuum cleaner is turned on the moon.

Q11. After reflection from a plane mirror the word will look like.

(a) AMBULANCE
(b) ECNALUBMA
(c) AMBULA CE
(d) AWBULANCE
Ans: (c) The image formed by a plane mirror is always virtual (meaning that the light rays do not actually come from the image), upright, and of the same shape and size as the object it is reflecting. A virtual image is a copy of an object formed at the location from which the light rays appear to come. However, the image is a laterally-inverted “mirror image” of the object. So we will get the word AMBULANCE after reflection.

Q12. A rubber ball is dropped from a height of 2 metres. To what height will it rise if there is no loss of energy/velocity after rebounding ?

(a) 4 metres (b) 3 metres
(c) 2 metres (d) 1 metre
Ans: (c) The potential energy of a body when raised through height h is given by mgh. Each time, a normal rubber ball hits the floor, it loses one-fifth of its total energy and the rebound height is proportional to energy, so each bounce will rebound to four-fifth of the previous bounce. But, the question states that there is no loss of energy/velocity after rebounding. So the height of 2 metres will be maintained.

Q13. When a pail of water is swung in a vertical circle, the water does not fall out at the top of the loop when the speed is

(a) below a certain minimum value irrespective of amount of water in the pail
(b) above a certain minimum value irrespective of amount of water in the pail
(c) above a certain minimum value depending on amount of water in the pail
(d) below a certain minimum value depending on amount of water in the pail
Ans: (b) When a pail of water is swung in a vertical circle, the water does not fall out at the top of the loop when the speed is great enough. At every point in the circle the water tries to fall vertically out due to the force of gravity g but also tries to move in a straight line due to its circular motion. If the velocity is large enough the water will not drop out of the bucket far enough before it is moved round the circle. The value of g does not depend upon the object’s mass.

Q14. Who enunciated the laws of planetary motion?

(a) Nicolaus Copernicus
(b) Johannes Kepler
(c) Isaac Newton
(d) Galileo
Ans: (b) Kepler’s laws of planetary motion are three scientific laws describing orbital motion, each giving a description of the motion of planets around the Sun. The laws are: the orbit of every planet is an ellipse with the Sun at one of the two foci; a line joining a planet and the Sun sweeps out equal areas during equal intervals of time; and the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

Q15. The radiant energy having lowest energy is

(a) gamma rays
(b) UV rays
(c) visible light
(d) microwave radiation
Ans: (d) The parts of the electromagnetic spectrum, arranged from highest energy to lowest, are gamma rays, Xrays, ultraviolet light, visible light, infrared light, microwaves, and radio waves.

Q16. Which one of the following has the highest value of specific heat?

(a) Glass (b) Copper
(c) Lead (d) Water
Ans: (d) The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius. The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation. The specific heat per gram for water is much higher than that for a metal.

Q17. A microscope used in pathological laboratories forms

(a) magnified, virtual, erect image
(b) diminished, real and erect image
(c) magnified, virtual and inverted image
(d) diminished, virtual and erect image
Ans: (c) A microscope is an instrument that produces a clear magnified image of an object viewed through it. A basic microscope is made up of two converging lenses. The first lens creates a real image which serves as the object for the second lens, and the image created by the second lens is the one a viewer sees. The final image is virtual and is inverted compared to the original object.

Q18. The velocity of sound is more in

(a) water (b) air
(c) steel (d) wood
Ans: (c) Sound travels at different speeds depending on what it is traveling through. Of the three mediums (gas, liquid, and solid) sound waves travel the slowest through gases, faster through liquids, and fastest through solids. They travel over 17 times faster through steel than through air.

Q19. The magnifying power of an astronomical telescope can be decreased by

(a) decreasing the focal length of the eyepiece
(b) increasing the focal length of the eyepiece
(c) increasing the focal length of the objective
(d) None of these
Ans: (b) The magnifying power (M) of astronomical telescope is given by M = focal length of objective/focal length of eye piece . This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.

Q20. Necessary element of change in solar energy to electric energy

(a) Berillium (b) Silicon
(c) Tantelum (d) Pure Copper
Ans: (b) A small solar electric or photovoltaic (PV) converts solar energy into electrical energy. Solar cells consist of semiconductor materials which work on photoelectric effect. Silicon remains the most popular material for solar cells.

Q21. Which of the following events occurred first ?

(a) Albert Einstein propounded the General Theory of Relativity
(b) Max Planck unveiled the Quantum Theory
(c) Marconi first tranmitted a wireless signal
(d) Madame Marie Curie became the first woman Nobel Prize winner
Ans: (b) General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907–1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.

Q22. The audio signals of TV are

(a) Amplitude modulated
(b) Frequency modulated
(c) Unmodulated
(d) Velocity modulated
Ans: (b) In analogue television, the sound portion of a broadcast is invariably modulated separately from the video. Most commonly, the audio and video are combined at the transmitter before being presented to the antenna, but in some cases separate aural and visual antennas can be used. In almost all cases, standard wideband frequency modulation is used.

Q23. Red light is used for signals because it has

(a) long wavelength
(b) high intensity
(c) high frequency
(d) low refraction in the medium
Ans: (a) Red is the international colour of stop signs and stop lights on highways and intersections because it is scattered the least by air molecules. The effect of scattering is inversely related to the fourth power of the wavelength of a colour. Red has the highest wavelength of all the colours and is able to travel the longest distance through fog, rain, and the alike.

Q24. Woollen cloth protects the body from cold because

(a) it is a good conductor of heat
(b) it is a poor conductor of heat
(c) external heat rays enter into the body through the woollen cloth
(d) it reflects heat
Ans: (b) It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.

Q25. The owl can see most clearly in total darkness because

(a) it has squint eyes
(b) it has large eyes with orbs directed forward, giving it binocular sight
(c) it has light bulbs in its eyes provided by nature
(d) it produces infrasonic sounds
Ans: (b) Because of their eyes, an owl can see much better in the dark than we can. Owls have very large eyes which maximize light gathering in conditions of minimum light, thereby enabling them to see at night. The orbs of their eyes are directed forward, giving them binocular vision. They are able to see their prey in a three-dimensional manner. However, an owl’s eye cannot rotate.

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