Physics MCQs

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A black body is an idealized physical body that absorbs all the incident electromagnetic radiation, regardless of frequency or angle of incidence. Another property is roughness. For example, sand is rough and black and so it is a good absorber of radiation.

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Heat is a form of energy. An important property of heat is that it flows from a body at higher temperature to another body at lower temperature. However, it may or may not travel with speed of light depending upon the temperature difference between source and sink.

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The pitch of a sound is determined by the frequency of vibration of the sound waves. So higher the frequency the higher is the pitch. Frequency is often measured in units called Hertz (Hz). If a sound source vibrates at 100 vibrations per second, it has a frequency of 100 Hertz.

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The momentum of a particle is given by the equation, P = mv, where P is the momentum of the particle, m is the mass of the particle, and v is the velocity of the particle. The kinetic energy of a particle is given by the equation, KE = . mv2. So, if momentum is doubled, kinetic energy increases four times.

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When the pendulum is taken to the moon, the value of ‘g’ will decrease and hence time period will increase than that of on the Earth.

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Persistence of vision is the phenomenon of the eye by which an afterimage persists for approximately one twenty-fifth of a second on the retina. In the early days of cinema, it was scientifically determined that a frame rate of less than 16 frames per second (frame/s) caused the mind to see flashing images. Audiences still interpret motion at rates as low as ten frames per second or slower, but the flicker caused by the shutter of a film projector is distracting below the 16-frame threshold.

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A compound microscope is a microscope which uses multiple lenses to collect light from the sample and then a separate set of lenses to focus the light into the eye or camera. The objective lens provides the primary magnification which is compounded (multiplied) by the ocular lens (eyepiece).

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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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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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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.