Physics MCQs

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The density of dry air is more than that of moist air. The speed of sound in a medium is inversely proportional to the square root of its density. Therefore, the speed of sound in moist air is more than that in dry air.

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The process of slow and uniform cooling of hot metals in metallurgy is known as annealing. It is a heat process whereby a metal is heated to a specific temperature /colour and then allowed to cool slowly. This softens the metal which means it can be cut and shaped more easily. Using annealing, mild steel is heated to a red heat and allowed to cool slowly.

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According to the Second law of Thermodynamics, heat transfer always occurs from a region/body of high temperature to another region/body of lower temperature. The process continues till the body and the surroundings reach the same temperature, at which point they are in thermal equilibrium. Transfer of thermal energy occurs mainly through conduction, convection or radiation.

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A solar cell, or photovoltaic cell, is an electrical device that converts sunlight directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. A photovoltaic cell is a specialized semiconductor diode electronic device. Individual solar cell devices can be combined to form modules, otherwise known as solar panels.

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The twinkling of primarily caused by atmospheric multiple refraction of light. The early sun rise and late sunset by 2 minutes each respectively is also because of atmospheric refraction of light. The appearing of the sun to be red at dawn and dusk is primarily because of scattering of light than refraction of hight. Red light is scattered the least among all colour of light present in the visible spectrum of white light.

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The phenomena such as interference, diffraction, and polarization can only be explained when light is treated as a wave whereas photoelectric effect, line spectra, and the production and scattering of x rays demonstrate the particle nature of light. The photoelectric effect supports a particle theory of light in that it behaves like an elastic collision (one that conserves mechanical energy) between two particles, the photon of light and the electron of the metal.

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Semiconductors are insulators at low temperatures and reasonably good conductors at higher temperatures. As temperature increases, the semiconductor material such as silicon, germanium, etc. becomes a better and better conductor compared to metallic conductor in which the resistance increases with increase in temperature.

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Laser, an acronym for Light Amplification by Stimulated Emission of Radiation, creates a radiation beam that is coherent (in-phase). In a coherent light source, the amplitude of the radiated waves is added that results in a radiation beam of great intensity. It normally produces only one or two wavelengths. The single wavelength is called monochromatic radiation.

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A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum. Cathode ray oscilloscope is an electronic display device containing cathode-ray tube (CRT) that generates an electron beam used to produce visible patterns or graphs on a phosphorescent screen. A sonometer is an apparatus made of hollow box having two holes. A string is attached to it by which the transverse vibrations of strings are studied.

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Gravitational waves are disturbances in spacetime, propagating at light speed. Gravitational lensing occurs when matter, like a galactic cluster, bends light from a source, magnifying it. Gravitational waves differ from gravity waves, which are generated in fluids by gravity, such as ocean waves caused by wind.