Physics GK Quiz-24

Physics GK Quiz-24

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

    461. When a detergent is added to pure water, its surface tension

    (1) increases
    (2) decreases
    (3) remains constant
    (4) becomes infinite
    Answer:
    461. (2) When Soaps and detergents are added to water, they weaken the strength of the skin on the water’s surface due to surface tension by interfering with hydrogen bonding between water molecules. It happens because the polar end of the soap or detergent is also attracted to the water, thereby
    decreasing the surface tension. 

    462. Ultra violet light of Sun’s radiation is prevented from reaching the earth’s atmosphere by the layer of

    (1) Oxygen
    (2) Hydrogen
    (3) Ozone 
    (4) Helium
    Answer:
    462. (3) The ozone layer is a layer in Earth’s atmosphere containing relatively high concentrations of ozone (O3). The layer absorbs 97–99% of the Sun’s mediumfrequency ultraviolet light (from about 200 nm to 315 nm wavelength), which potentially damages exposed life forms on Earth.

    463. White clothes are cooler than black ones because they

    (1) absorb all the light that reaches them
    (2) reflect all the light that reaches them
    (3) will not allow the light to penetrate
    (4) cool the sunlight completely
    Answer:
    463. (2) The coolness and warmth associated with clothes is because of their reflective or absorptive capacities. White clothes are good reflectors of light, thereby keeping the body cool. The opposite is the case with black clothes.

    464. The primary colours in photography are

    (1) Red, Blue, Yellow
    (2) Red, Yellow, Green
    (3) Red, Blue, Green
    (4) Blue, Yellow, Green
    Answer:
    464. (1) There are three primary colours of Red, Green and Blue (RGB). As these are mixed they form lighter colours, and when all three are mixed together they appear as white. Artists and graphic designers, who work with paintings and illustrations more than they do with photographs, often refer to Red, Yellow and Blue as the primary colours.

    465. A concave lens always forms

    (1) a real image
    (2) a virtual image
    (3) an image type which depends on object characteristics
    (4) an image type which depends on lens curvature
    Answer:
    465. (2) Concave lens always form the virtual and erect image and the image is always diminished. Convex lens forms real image as well as virtual image. It forms both enlarged image and the diminished image.

    466. The blue colour of sky is due to

    (1) reflection of sunlight
    (2) refraction of sunlight
    (3) scattering of shorter wavelengths of sunlight in the atmosphere
    (4) scattering of longer wavelengths of sunlight in the atmosphere
    Answer:
    466. (3) The blue colour of the sky is caused by the scattering of sunlight off the molecules of the atmosphere. This scattering, called Rayleigh scattering is more effective at short wavelengths (the blue end of the visible spectrum). Therefore the light scattered down to the earth at a large angle with respect to the direction of the sun’s light is predominantly in the blue end of the spectrum.

    467. Metal tea pots have wooden handles because

    (1) wood is a bad conductor of heat
    (2) it prevents electric shock
    (3) it gives beauty to the pots
    (4) it is hygienic
    Answer:
    467. (2) Wood is a bad conductor of heat due to the arrangement of its molecules. As the molecules of
    wood are far from each other, they cannot pass heat through them.

    468. Ozone layer above the surface of Earth provides a shield against

    (1) X-rays
    (2) Ultra-violet rays
    (3) Gamma rays
    (4) Infra-red rays
    Answer:
    468. (2) The Ozone layer absorbs 97–99% of the Sun’s medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which potentially damages exposed life forms on Earth.

    469. The Newton’s First Law is also called as

    (1) Law of moments
    (2) Law of inertia
    (3) Law of energy
    (4) Law of momentum
    Answer:
    469. (2) According to Newton’s first law, an object that is at rest will stay at rest unless an unbalanced force acts upon it and an object that is in motion will not change its velocity unless an unbalanced force acts upon it. So this law is known as the law of inertia.

    470. If we want to calculate the pressure of a liquid at the bottom of a vessel, the quantity which is not required to determine it, is

    (1) Height of the liquid column
    (2) Surface area of the bottom of the vessel
    (3) Density of the liquid
    (4) Acceleration due to gravity at the bottom of the vessel
    Answer:
    470. (2) The pressure exerted by a static fluid depends only upon the depth of the fluid, the density of the fluid, and the acceleration of gravity. The pressure in a static fluid arises from the weight of the fluid and is given by the expression Pstatic fluid = dgh, where d= fluid density, g= acceleration due to gravity and h= depth of fluid. Static fluid pressure does not depend on the shape, total mass, or surface area of the liquid.

    471. The water from a hand pump is warm in winter because

    (1) Our body is cold in winter and the water appears to be warm
    (2) The temperature inside the earth is higher than the atmospheric temperature
    (3) The pumping process causes friction which warms up the water
    (4) Inside water comes out and absorbs heat from the environment
    Answer:
    471. (2) In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.

    472. A water tank appears shallower when it is viewed from top due to

    (1) rectilinear propagation of light
    (2) reflection
    (3) total internal reflection
    (4) refraction
    Answer:
    472. (4) This phenomenon is because of refraction of light. The lines of sight intersect at a higher position than where the actual rays originated. This causes the water to appear shallower than it really is. The depth that the water appears to be when viewed from above is known as the apparent depth.

    473. For a ray of light to suffer total internal reflection it has to pass from :

    (1) glass to water
    (2) water to glass
    (3) air to water
    (4) air to glass
    Answer:
    473. (3) Total internal reflection is an optical phenomenon that happens when a ray of light strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. This can only occur where light travels from a medium with a higher [n1=higher refractive index] to one with a lower refractive index [n2=lower refractive index]. Total internal reflection can be seen at the air-water boundary.

    474. A stone is dropped from the roof of a house towards the ground. The kinetic energy of the stone will be maximum:

    (1) just after it is dropped
    (2) when it is just on the half-way
    (3) just before it touches the ground
    (4) when it touches the ground
    Answer:
    474. (3) When an object reaches the ground it has its maximum value of kinetic energy just before touching the ground. Since kinetic energy + potential energy= Constant; so on reaching ground the potential energy of an object becomes zero (0). The kinetic energy on reaching ground becomes maximum.

    475. A black body can absorb radiations of ;

    (1) lower wavelengths only
    (2) intermediate wavelengths only
    (3) higher wavelengths only
    (4) all wavelengths
    Answer:
    475. (4) A black body is a theoretical object that absorbs 100% of the radiation that hits it. Therefore it reflects no radiation and appears perfectly black. At a particular temperature the black body would emit the maximum amount of energy possible for that temperature. This value is known as the black body
    radiation. It would emit at every wavelength of light as it must be able to absorb every wavelength to be
    sure of absorbing all incoming radiation.

    476. Hydraulic machines work under the Principle of :

    (1) Newton’s Law
    (2) Joules Law
    (3) Pascal’s Law
    (4) Floatation Law
    Answer:
    476. (3) Hydraulic Machinery refer to machines and equipment which use high pressure fluid to accomplish any work in industrial fields. These machines work on the basis of Pascal’s Law which says “The pressure, in a static hydraulic fluid in a closed system is everywhere the same”.

    477. The Newton’s First Law is also called as

    (1) Law of moments
    (2) Law of inertia
    (3) Law of energy
    (4) Law of momentum
    Answer:
    477. (2) According to Newton’s first law, an object that is at rest will stay at rest unless an unbalanced force acts upon it and an object that is in motion will not change its velocity unless an unbalanced force acts upon it. So this law is known as the law of inertia.

    478. If we want to calculate the pressure of a liquid at the bottom of a vessel, the quantity which is not required to determine it, is

    (1) Height of the liquid column
    (2) Surface area of the bottom of the vessel
    (3) Density of the liquid
    (4) Acceleration due to gravity at the bottom of the vessel
    Answer:
    478. (2) The pressure exerted by a static fluid depends only upon the depth of the fluid, the density of the fluid, and the acceleration of gravity. Static fluid pressure does not depend on the shape, total mass,
    or surface area of the liquid.

    479. The water from a hand pump is warm in winter because

    (1) Our body is cold in winter and the water appears to be warm
    (2) The temperature inside the earth is higher than the atmospheric temperature
    (3) The pumping process causes friction which warms up the water
    (4) Inside water comes out and absorbs heat from the environment
    Answer:
    479. (2) In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.

    480. A water tank appears shallower when it is viewed from top due to

    (1) rectilinear propagation of light
    (2) reflection
    (3) total internal reflection
    (4) refraction
    Answer:
    480. (4) This phenomenon is because of refraction of light. The lines of sight intersect at a higher position than where the actual rays originated. This causes the water to appear shallower than it really is.

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