General Science - Physics MCQs

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The first thing we have to note is that light bends when it changes medium, but when light changes the medium, it is always NOT necessary that it bends too. In this question, you have to remember that speed changes and also the wavelength may change but not the frequency. Change in speed is the fundamental of refraction. Refraction is the change in direction of a wave due to a change in its speed. Due to change of medium, the phase velocity of the wave is changed but its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any angle other than 90° or 0°. If the wave passes at 90°, it’s speed will still change, its refraction would still occur but its direction will not change. This is funda behind use of lenses. Refraction is described by Snell’s law, which states that for a given pair of media and a wave with a single frequency, the ratio of the sines of the angle of incidence ?1 and angle of refraction ? 2 is equivalent to the ratio of phase velocities (v1 / v2) in the two media, or equivalently, to the opposite ratio of the indices of refraction (n2 / n1). Please note that refraction is a phenomenon that often occurs when waves travel from a medium with a given refractive index to a medium with another at an oblique angle. At the boundary between the media, the wave’s phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases but its frequency remains constant. For example, a light ray will refract as it enters and leaves glass, assuming there is a change in refractive index. A ray traveling along the normal (perpendicular to the boundary) will change speed, but not direction. Refraction still occurs in this case.

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The Classical Physics includes the study of phenomena involving objects having finite size on terrestrial and astronomical scale. It includes subjects like Optics, Thermodynamics, Mechanics and Electrodynamics

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Gravitational Forces are the weakest forces in nature. They obey inverse square law as they vary inversely as the square of the distance between the two bodies. They are central forces and conservative forces. They operate over very long distances having an infinite range.

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Following are the basic characteristics of an inelastic collision: 1. Linear momentum is conserved 2. Kinetic energy is NOT conserved 3. Total energy is conserved 4. Some or all the forces involved may be non-conservative in nature

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Characteristics of Gravitational Forces:

1. It is always attractive in nature.
2. It is independent of the medium between the bodies.
3. It holds good over a wide range of distances
4. It is a central force i.e. acts along the line joining the centres of two interacting bodies
5. The gravitational force between two particles is independent of the presence or absence of other bodies
6. It is the weakest force in nature.
7. It is a conservative force i.e. work done by it is path independent or work done in moving a particle round a closed path under the action of gravitational force is zero.
8. It is an action-reaction pair.

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The gravitational potential energy of a body at a point is defined as the amount of work done in bringing the body from infinity to that point against the gravitational force. U = – GMm/r When r =infinity, then U =0

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The value of acceleration due to gravity decreases with increase in height. Therefore, it is lesser at mountains than in plains.

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The weight of a body is the force with which it is attracted towards the centre of earth. Weightlessness is a situation when the observed weight of the body becomes zero. Some of the situations of state of weightlessness are: 1. When objects fall freely under gravity 2. When a satellite revolves in its orbit around the earth 3. When bodies are at null points in outer space

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The gravitational force between two objects depends on the Gravitational constant, Distance between the objects and Product of the masses of the objects. F = Gravitational constant x (Product of the masses of the objects) / Square of Distance between the objects

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The value of acceleration due to gravity vary due to the following factors : (a) Shape of the earth (b) Height above the earth surface (c) Depth below the earth surface (d) Axial rotation of the earth