Physics GK Quiz-16

Physics GK Quiz-16

Physics Multiple Choice Questions (MCQs) Quiz for State and UPSC Civil Services Examinations. Objective Questions on Physics for competitive examinations.

    301. After long periods of use, a grey spot develops on the inside of a bulb. This is because

    (1) the tungsten filament evaporates and collects there
    (2) the heat of the bulb scorches the glass at the top
    (3) dust inside the bulb condenses on the top
    (4) glass undergoes a change due to the heat
    Answer:
    301. (3) 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.

    302. Should cars have bumpers that collapse under impact?

    (1) Yes, since the offending car should get damaged and pay for the mistake
    (2) No, since it would be very expensive to get the car repaired
    (3) No, since the colliding car would then ram into the occupants and kill them
    (4) Yes, since they help to absorb the impact of a collision and keep the occupants safe
    Answer:
    302. (4) 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.

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

    (1) at a higher level in water
    (2) at a higher level in alcohol
    (3) at the same level in both
    (4) floating in alcohol and sinking in water
    Answer:
    303. (1) 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.

    304. 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

    (1) behind the retina
    (2) in front of the retina
    (3) on the retina
    (4) on the blind spot
    Answer:
    304. (2) 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.

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

    (1) It provides oxygen to a drowning person
    (2) It increases the volume of the person to keep him afloat
    (3) It decreases the volume of the person to keep him afloat
    (4) The person can sit on it like a raft
    Answer:
    305. (2) 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.

    306. Myopia is the same as

    (1) Near sightedness
    (2) Astigmatism
    (3) Presbyopia
    (4) Long sightedness
    Answer:
    306. (1) 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.

    307. Sun’s heat reaches us by

    (1) Conduction
    (2) Convection
    (3) Radiation
    (4) Reflection
    Answer:
    307. (3) 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.

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

    (1) in the same time
    (2) with the same speed
    (3) in the same time with the same speed
    (4) in the same time with the same kinetic energy
    Answer:
    308. (2) 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.

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

    (1) To prevent the steam pressure from bursting open the pouch
    (2) To allow the heat to get into the food through the hole
    (3) To allow the microwaves to get into the food through the holes
    (4) To allow the aroma of the food to come out through the holes
    Answer:
    309. (1) 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.

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

    (1) work as efficiently as on the earth
    (2) not work at all
    (3) work with reduced efficiency
    (4) work with increased efficiency
    Answer:
    310. (2) 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.

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

    (1) AMBULANCE
    (2) ECNALUBMA
    (3) AMBULA CE
    (4) AWBULANCE
    Answer:
    311. (3) 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.

    312. 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 ?

    (1) 4 metres
    (2) 3 metres
    (3) 2 metres
    (4) 1 metre
    Answer:
    312. (3) 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.

    313. 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

    (1) below a certain minimum value irrespective of amount of water in the pail
    (2) above a certain minimum value irrespective of amount of water in the pail
    (3) above a certain minimum value depending on amount of water in the pail
    (4) below a certain minimum value depending on amount of water in the pail
    Answer:
    313. (2) 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.

    314. Who enunciated the laws of planetary motion?

    (1) Nicolaus Copernicus
    (2) Johannes Kepler
    (3) Isaac Newton
    (4) Galileo
    Answer:
    314. (2) 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.

    315. The radiant energy having lowest energy is

    (1) gamma rays
    (2) UV rays
    (3) visible light
    (4) microwave radiation
    Answer:
    315. (4) 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.

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

    (1) Glass 
    (2) Copper
    (3) Lead 
    (4) Water
    Answer:
    316. (4) 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.

    317. A microscope used in pathological laboratories forms

    (1) magnified, virtual, erect image
    (2) diminished, real and erect image
    (3) magnified, virtual and inverted image
    (4) diminished, virtual and erect image
    Answer:
    317. (3) 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.

    318. The velocity of sound is more in

    (1) water 
    (2) air
    (3) steel 
    (4) wood
    Answer:
    318. (3) 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.

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

    (1) decreasing the focal length of the eyepiece
    (2) increasing the focal length of the eyepiece
    (3) increasing the focal length of the objective
    (4) None of these
    Answer:
    319. (2) 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.

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

    (1) Berillium 
    (2) Silicon
    (3) Tantelum 
    (4) Pure Copper
    Answer:
    320. (2) 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.

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