Physics MCQs

Notes:
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.

Notes:
Carbon dioxide is a greenhouse gas that absorbs heat radiated from the Sun as well as re-radiated heat from the Earth’s surface. It not only retains the solar radiation, but, absorbs thermal infrared energy (heat) radiated by the surface. It absorbs thermal infrared energy with wavelengths in a part of the energy spectrum that other gases do not. It is believed to have played an important effect in regulating Earth’s temperature throughout its 4.7-billion-year history.

Notes:
One joule is equal to 0.2390 calorie. Joule is equal to the energy transferred to (or work done on) an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre (1 newton metre or N’m). It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second.

Notes:
Scintillation or twinkling is generic terms for variations in apparent brightness or position of a distant luminous object viewed through a medium. One of the three principal factors governing astronomical seeing, atmospheric scintillation is defined as variations in illuminance only. Scintillation does not cause images of planets to flicker. Most scintillation effects are caused by anomalous refraction caused by small-scale fluctuations in air density usually related to temperature gradients.

Notes:
Red light has a longer wavelength than violet light and the other colours of visible light have intermediate wavelengths. As light passes from air into glass, there is reduction of velocity. Due to longer wavelengths, red waves travel fastest and is refracted the least, while violet waves travel the slowest and is refracted the most because of their smaller wave length.

Notes:
The lens is composed of transparent, flexible tissue and is located directly behind the iris and the pupil. It is the second part of our eye, after the cornea. The lens bends light coming into the eye to help focus it on the retina.

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When the sun’s rays falling on concave mirror, these are reflected so as converge to a point called the focus of mirror. Since concave mirror can concentrate sun’s rays falling on it at one point, it can be used as burning glass. It is because of this property that concave mirrors are used in solar cookers. A flat mirror does not have a focal point. It does regular reflection off all of its points.

Notes:
Angle of incidence is the angle between an incident ray and the normal. Angle of refraction is the angle between a refracted ray and the normal. When the angle of refraction is equal to 90°, the angle of incidence is called the critical angle. In this case, the light ray goes from denser to rarer medium.

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Ebonite is the hard product obtained on vulcanizing natural rubber. Ebonite is used for making battery cases, electrical switchboard panels, plugs and sockets, telephone receivers etc. rubber is not a conductor electricity.

Notes:
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.