Practice MCQ Questions and answers on Physics-GK

Sound waves in air (and any fluid medium) are longitudinal waves because particles of the medium through which the sound is transported vibrate parallel to the direction that the sound wave moves. A vibrating string can create longitudinal waves as depicted in the animation below.

You see that the field lines near the center are parallel to the length of the bar. Moreover, the density of the field lines on the picture is maximized at the "poles" of the bar magnet and minimized at the center which means that the magnitude of the magnetic field is smallest at the center, too. It's not hard to see why the field lines look approximately as those on the picture above. For an infinitely long magnet, the magnetic field would be fully confined to the cylinder - think of an infinitely long solenoid which essentially has the same magnetic field as a bar magnet. For a bar magnet of a finite length, the field lines ultimately split behind the poles but they're still comparably strong over there. On the other hand, the field outside the bar, and far from the poles, is only nonzero because of some subleading effects; it would vanish for an infinitely long solenoid - that's why the field is so small over there.

In physics, friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. When walking, the friction between the ground and the feet is crucial for maintaining stability and propulsion.

Option A: While it's true that sand is soft and concrete is hard, the question is specifically asking about the difficulty of walking on each surface, which relates more to friction than hardness.
Option B: Sand has a lower coefficient of friction compared to concrete. This means that there is less resistance between the feet and the sand, making it more difficult to walk on a sandy road as compared to a concrete road where the friction between the feet and concrete is greater, providing better traction and stability.
Option C: This is the opposite of the correct explanation. If the friction between sand and feet were more than that between concrete and feet, walking on sand would be easier, not more difficult.
Option D: The texture of the surfaces (grainy sand versus smooth concrete) might play a role in perception, but the primary factor affecting difficulty in walking is the friction between the surfaces and the feet, as explained in option B.

Therefore, the correct answer is Option B: the friction between sand and feet is less than that between concrete and feet.

14 m/s.

The amplitude (A) is independent of other means it is not related to the other quantities.

The SI unit of intensity of illumination (illuminance) is the lux. An illuminance of 1.0 lux is produced by 1.0 lumen of light shining on an area of 1.0 m².

On a rainy day, small oil films on water show brilliant colours. This is due to Interference.
Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater, lower or same amplitude.

Since we know that electric currents move from a higher potential or a lower potential. Also, electrons move in the direction opposite to electric current. So the electron on the line joining two points A and B will move from lower to higher potential i.e, it will move towards B.

The material of rain proof coats have the property of not minimizing the surface tension which will tend the water molecule to be in its drop form.

RADAR is used for detecting and locating the position of objects such as Aeroplanes.