Physics MCQs

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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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Mach number is a ratio of the speed of a body (aircraft) to the speed of sound in the undisturbed medium through which the body is traveling. Mach 1 is equal to the speed of sound (which is 332 m/s or 1195 km/hr. ) An aircraft flying at Mach 2 is flying at twice the speed of sound in air, etc.

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Pascal’s law states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container. Pressure is the force on an object that is spread over a surface area. The equation for pressure is the force divided by the area where the force is applied.

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Lambert’s Law states that the intensity of emitted light from a surface is directly proportional to the cosine of the angle between the line of view and the normal to the surface. A Lambertian surface is a surface that follows this rule exactly. In practice, most surfaces are not perfectly Lambertian. A surface which obeys Lambert’s law is said to be Lambertian, and exhibits Lambertian reflectance. Such a surface has the same radiance when viewed from any angle.

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Flint glass is optical glass that has relatively high refractive index and low Abbe number (high dispersion). A concave lens of flint glass is commonly combined with a convex lens of crown glass to produce an achromatic doublet lens because of their compensating optical properties, which reduces chromatic aberration (colour defects).

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Image quality is a characteristic of an image that measures the perceived image degradation (typically, compared to an ideal or perfect image). of an image determines the amount of detail an image can convey. System sharpness is affected by the lens (design and manufacturing quality, focal length, aperture, and distance from the image center) and sensor (pixel count and anti-aliasing filter).

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Convex mirror is also known as diverging mirror as this mirror diverges light when they strike on its reflecting surface. Virtual, erect and diminished images are always formed with convex mirrors, irrespective of the distance between the object and the mirror. Apart from other applications, convex mirror is mostly used as rear view mirror in vehicles.

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Magnetic keepers are pieces of soft iron that are placed across the poles of a bar magnet or a horseshoe magnet. They help prevent the loss of magnetism. i.e. help retain the magnetic strength of the magnates placed together.

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Silver has the highest electrical conductivity 6.3×10⁷ m/ohm at 20°C. Silver has the highest electrical conductivity of all metals.

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Magnetic resonance imaging (MRI), nuclear magnetic resonance imaging (NMRI), or magnetic resonance tomography (MRT) is a medical imaging technique used in radiology to visualize internal structures of the body in detail. MRI makes use of the property of nuclear magnetic resonance (NMR) to image nuclei of atoms inside the body. An MRI scanner is a device in which the patient lies within a large, powerful magnet where the magnetic field is used to align the magnetization of some atomic nuclei in the body, and radio frequency fields to systematically alter the alignment of this magnetization. This causes the nuclei to produce a rotating magnetic field detectable by the scanner. and this information is recorded to construct an image of the scanned area of the body.