Physics MCQs

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In photography, shutter speed or exposure time is the effective length of time a camera’s shutter is open to let light enter into camera . The total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor. The correct exposure for a particular object depends on the brightness of the object to be photographed.

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The human eye is sensible to light having wavelength roughly between 400 nm and 700 nm. When illumination is enough (in daylight) the maximum sensitivity is in the green region at 555 nm. However, human eyes are the most sensitive to yellow colour light.

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Optical filters are devices that selectively transmit light in a particular range of wavelengths, that is, colors, while blocking the remainder. They are commonly used in photography (where some special effect filters are occasionally used as well as absorptive filters), fluorescence microscopy, spectroscopy, clinical chemistry, coloured stage lighting, etc.

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A concave mirror can form diminished as well as enlarged images, depending upon the distance of the object from the mirror. The image can be real and inverted or virtual and erect. While a convex mirror always forms a virtual, erect and diminished image, irrespective of the distance of the object from the mirror.

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Different types of images can be formed by a concave mirror by changing the position of the object from the concave mirror. When object is placed between infinity and centre of curvature of a concave mirror the image is formed between centre of curvature (C) and focus (F).

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Incandescent light bulbs consist of an air-tight glass enclosure with a filament of tungsten wire inside the bulb, through which an electric current is passed. Tungsten is used because it has the highest melting point (>3400 degrees C) of any metal.

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When a non-relativistic electron and a non-relativistic proton move having the same de Broglie wavelength, then they will have the same linear momentum p = mv. If the electron and proton have the same momentum, they cannot have the same speed because of the difference in their masses. An electron and photon can have the same wavelength since the wavelength of electron can be changed by changing its velocity.

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Electrons revolve around the nucleus in circular orbits of all possible radii. The necessary centripetal force for circular motion of electrons around the nucleus is provided by electrostatic force of attraction between electrons and nucleus.

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The roentgen equivalent man (REM) is a CGS unit of equivalent dose, effective dose, and committed dose, which are dose measures used to estimate potential health effects of low levels of ionizing radiation on the human body.

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In physics, electromagnetic radiation (EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma radiation only.