Physics MCQs

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A concave lens is a type of lens that has a thinner center than edges, and it is sometimes called a diverging lens because it spreads out light rays that are parallel to its axis. The focal length of a lens is a measure of its ability to focus light, and it is defined as the distance from the lens to the point where the light rays converge. In the case of a concave lens with a power of -5D, the focal length would be equal to 1/5 of a meter, or 20 centimeters.

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The sunlight that reaches the earth has ultraviolet A and ultraviolet B (UVA and UVB) rays. These ultraviolet rays are the main causes of damage to the skin from the sun. UVA and UVB rays affect the skin’s sensitivity to sun exposure in different ways.

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In 1647 the French scientist Blaise Pascal (1623–1662) discovered that water exerts the same pressure in all directions. This statement is known as Pascal’s Principle.
Pascal’s law states that increase in pressure at a point in the enclosed liquid in equilibrium is transmitted equally in all directions in liquid and to the Walls of the container. The working of hydraulic lift, hydraulic press and hydraulic brakes are based on Pascal’s law.

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Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies as high as 300 gigahertz to as low as 30 hertz. It is used to measure the speed of an approaching car.

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Inertia is the resistance experienced by an object to any change in its velocity. This includes changes to the object’s speed, or direction of motion. Inertia of rest, Inertia of motion are the examples.

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Ultrasound corresponds to sound waves with frequencies exceeding the upper limit of human perceptible sound, generally above 20 kHz. Humans, typically, can perceive sounds ranging between 20 Hz and 20 kHz. Ultrasound, therefore, is beyond the auditory range of humans and is employed in technologies like medical imaging and sonar devices due to its unique properties.

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Gamma rays is commonly used in gemstone industry to change white topaz into blue topaz. Because white topaz is heat-treated to turn into blue topaz, the value of blue topaz is often decreased.

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To calculate the distance of the object from the source of sound based on the time taken for the echo, we can use the formula for distance traveled by sound:

Distance = (Speed of Sound × Time) / 2

The speed of sound in air at normal room temperature (20°C) is approximately 343 meters per second (m/s).

Given that the time taken in the echo is 5 seconds, we can plug the values into the formula:

Distance = (343 m/s × 5 s) / 2 Distance = 1715 meters / 2 Distance ≈ 857.5 meters

So, the approximate distance of the object from the source of sound is approximately 857.5 meters.

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The Corpuscular theory of light was given by Isaac Newton. It was replaced by Huygens’ wave theory when it failed to adequately explain the diffraction, interference and polarization of light. The Huygens’ wave theory was replaced by Planck’s quantum theory and finally de-Broglie’s Dual-Theory of light replaced all previous ones.

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The physical quantities which have only magnitude and no direction are called as Scalar quantities. Some examples of Scalar quantities: Work, Mass, Temperature, Distance, Speed.