Physics MCQs

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Astigmatism is due to imperfect spherical nature of eye lens. The focal length of eye lens is in two orthogonal directions become different so they cannot see objects in two orthogonal directions simultaneously. This defect in direction can be removed by using cylindrical lens in a particular direction.

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The latent heat Latent heat is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process. It causes change in state or phase but not in temperature.

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The correct answer is Quantum Theory. Black body radiation refers to the electromagnetic radiation emitted by an idealized object that absorbs all incident radiation. Max Planck introduced the concept in 1900, leading to the development of quantum mechanics. This theory explains that energy is quantized, emitted in discrete packets called quanta or photons, resolving the ultraviolet catastrophe predicted by classical physics.

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Atmospheric pressure is the force that causes liquid to rise in a syringe when the piston is pulled up. When the syringe is placed with its opening in a liquid and the plunger is pulled up, the air pressure inside the barrel becomes much less than the atmospheric pressure acting on the liquid. Fluids flow from a high pressure area to a low pressure area. Once the pressure inside the syringe is lower than the pressure outside the syringe, the fluid will flow into the syringe.

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Voltmeter is an instrument for measuring electric charge or electrical potential difference. It was invented by Hans Christian Oersted.

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A Balloon filled with a gas such as Hydrogen gas is much lighter in weight than the weight of air displaced by it. So the buoyant force exerted by the air on a balloon is greater than the weight of the balloon. The hydrogen gas which is lighter than air enables the balloon to float.

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When we shout in an empty hall, we hear your own sound after a short time. This is because the empty room reflects the sound, so there is an echo.
When a hall is full of people, the sound produced is reflected multiple times by the people. This causes the sound to overlap with the original sound, so the listener can’t distinguish between the two.
For an echo to be heard, the surfaces need to reflect the sound, or there needs to be more clarity. For example, big open spaces are good for hearing echoes.

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bar, torr and Pascal are the units used for measuring pressure whereas shake is a unit of time. 1 bar = 10⁵ Pa 1 bar = 760 torr 1 bar = 1 atmospheric pressure Shake is the smallest practical unit of time. 1 shake = 10^-8s

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The physical quantities which have both magnitude and direction are called as Vector quantities. Some examples of Vector quantities: Acceleration, Velocity, Torque, Displacement, Gravitational Intensity, Force.

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The force acting on a body for a short time are called as Impulse. Example: hitting a ball with a bat. Impulse = average force x time It is a measure of total effect of the force. Its unit is Ns