Physics MCQs

Notes:
Perceived loudness of sound is a psycho-acoustic quantity that depends on sound pressure level, the frequency spectrum, and the time behavior of the sound. The sone is a unit of perceived loudness that was proposed by Stanley Smith Stevens in 1936.Being a unit of how loud a sound is perceived, the sone scale of loudness is based on data obtained from subjects who were asked to judge the loudness of pure tones and noise. One sone is arbitrarily set equal to the loudness of a 1,000-hertz tone at a sound level of 40 decibels.

Notes:
A flying jet possesses both potential and kinetic energies. When it is in flight, it flies at a certain height above the ground and so it is displaced by certain distance and hence it possesses potential energy (energy that is stored because of the position of an object). Besides, it possesses kinetic energy as it is in motion.

Notes:
When the ball is on the ground there and not moving there is no potential energy or kinetic energy. When it is thrown upwards, at the top most position or height its velocity is zero and maximum energy is potential energy but as the ball falls to the ground that potential energy is converted to kinetic energy.

Notes:
Friction between two surfaces can be reduced by polishing them. The interlocking and projections are minimized by this method. Friction can also be reduced by applying lubricants between the contact surfaces to fill the fine pores or depressions in the surfaces and make them smooth. Friction does not depend on the area of contact.

Notes:
Force is the mass of an object, multiplied by its acceleration. In other words, F = ma, where m= mass of the object and a= acceleration of the object. Acceleration is the change in the velocity, divided by the time. So, according to the question, a = (18.6)/3 = 12/3 = 4 meters per second. Using the values of mass and acceleration, we get F= 6×4= 24 Newton.

Notes:
Transition metal ions which are mostly coloured except for zinc and scandium have an incomplete set of 3d electrons. Changes in the energy of these electrons correspond to the energy of visible light. The absorption of visible light by these ions lend colour to gems.

Notes:
The retina is the thin light-sensitive membrane lining the inner eyeball-towards the back of the eye. As our eye lens are convex in nature, they form mostly real, diminished i. e. reduced size and inverted images on the retina. When the images formed are real and inverted, the message sent by the optic nerve are chemical impulses which turn them into erect images that we see.

Notes:
Refraction of light is the change in direction (bending of light rays) when it passes from one optically transparent medium to another. During sunrise, when the sun is just below the horizon, the atmosphere causes the light rays to bend and see the sun early. Similarly, at sunset, the apparent position of the sun is visible and not the actual position due to the same bending of light rays effect. The apparent displacement of a pencil, partly immersed in water is also due to refraction.

Notes:
Focal length increases as the lens on the eye is contracted or relaxed by the ciliary muscles is because of the ability of the eye to accommodate. The ability of the eye to change the focus between objects at different distances by altering the curvature of the lens is called accommodation.

Notes:
The amount of light entering the eye is controlled by a reflex action. The size of the pupil changes in response to bright or dim light. This is controlled by the muscles of the iris.