Physics is the fundamental science that explores the nature of matter, energy, space, and time. It investigates everything from subatomic particles to the large-scale structure of the universe. Read more
What is the unit of Magnetic Flux?
HardThe Weber (Wb) is the SI unit of magnetic flux. It represents the total amount of magnetic field passing through a given area. One Weber is equal to one Tesla-meter squared 1 Wb = 1 Tcdotm^2.
The unit is named after Wilhelm Eduard Weber, a German physicist who co-invented the first electromagnetic telegraph!
What is the frequency range of human hearing?
MediumThe standard frequency range of human hearing is typically 20 Hz to 20,000 Hz 20 kHz. Sounds below 20 Hz are called infrasound, and sounds above 20,000 Hz are called ultrasound.
As people age, they gradually lose the ability to hear higher frequencies, which is why some "teenager-repellent" alarms use high-pitched sounds only young people can hear!
What does a convex lens do to light rays?
MediumA convex lens (also known as a converging lens) is thicker in the middle than at the edges and causes parallel light rays that pass through it to converge at a single point called the "focal point." These lenses are used to correct farsightedness and are the primary components in magnifying glasses, cameras, and telescopes.
Because they focus light to a single point, a convex lens can be used to concentrate sunlight enough to start a fire!
Which instrument measures atmospheric pressure?
MediumA barometer is a scientific instrument used to measure atmospheric pressure. Changes in air pressure are often used in weather forecasting to predict storms or clear skies. Evangelista Torricelli is credited with inventing the mercury barometer in 1643.
"High" pressure usually brings sunny, clear weather, while "low" pressure often signals that clouds and rain are on the way!
What is the SI unit of electric current?
MediumThe Ampere (often shortened to "Amp" or symbol A) is the SI unit of electric current. It measures the rate of flow of electric charge through a circuit. One ampere is equal to one "Coulomb" of electrical charge passing a point in one second. It was named after Andr?-Marie Amp?re, a French physicist who is considered the father of electromagnetism.
It only takes a very small amount of current to be dangerous to humans; while a 12-volt car battery has a lot of energy, even a tiny current of 0.1 to 0.2 Amperes passing through the heart for a second is enough to cause a fatal shock.
Which color of light has the shortest wavelength?
HardIn the visible light spectrum, violet light has the shortest wavelength, ranging from about 380 to 450 nanometers. Because wavelength and frequency are inversely related, violet light also has the highest frequency and the most energy of any color we can see. Colors with even shorter wavelengths, like ultraviolet, are invisible to the human eye.
Some animals, like bees and reindeer, can actually see ultraviolet light, which helps them find flowers or spot predators in the snow!
What is the SI unit of force?
EasyThe Newton (N) is the SI unit of force, named after Sir Isaac Newton in recognition of his laws of motion. One Newton is defined as the amount of force required to accelerate a mass of one kilogram at a rate of one meter per second squared 1 N = 1 kgcdotm/s^2. It is used to measure everything from the weight of an object to the thrust of a rocket.
To get a feel for the unit, one Newton is roughly equivalent to the weight of a small apple sitting in your hand!
What is a line on a map connecting points of equal pressure?
HardAn isobar is a line on a weather map that connects points of equal atmospheric pressure. Meteorologists use isobars to identify areas of high and low pressure, which helps them predict wind speed and direction.
The closer together the isobars are on a map, the stronger the wind is blowing in that area!
Which law states energy cannot be created or destroyed?
HardThe Law of Conservation of Energy, also known as the First Law of Thermodynamics, states that the total energy of an isolated system remains constant; energy can be transformed from one form to another (such as potential to kinetic), but it can never be created or destroyed. This is a fundamental principle of physics that applies to everything from a bouncing ball to a dying star.
Because of this law, a "Perpetual Motion Machine"-a machine that runs forever without an external energy source-is physically impossible. Every machine loses some energy to friction or heat, and since new energy cannot be "created" to replace it, the machine must eventually stop.
What is the boiling point of water (°C)?
EasyThe boiling point of water is 100^circC 212^circF at standard atmospheric pressure at sea level. Boiling occurs when the vapor pressure of the liquid equals the external pressure surrounding the liquid. Because atmospheric pressure decreases as you go higher, the boiling point of water also drops at higher altitudes.
If you were standing on the top of Mount Everest, water would boil at only 71^circC 160^circF. This means it is nearly impossible to make a "proper" hot cup of tea at the summit because the water isn't hot enough to extract the flavor before it starts boiling away!
Which wave requires a medium to travel?
EasyMechanical waves, such as sound waves or water waves, require a medium (solid, liquid, or gas) to travel through. They work by causing the particles in the medium to vibrate and pass energy to their neighbors. This is why sound cannot travel through the vacuum of space-there are no particles to carry the vibrations.
This means the famous movie tagline "In space, no one can hear you scream" is scientifically 100% accurate!
What is the boiling point of water in Kelvin?
MediumThe boiling point of water is 373.15 Kelvin (which is equal to 100^circCelsius or 212^circFahrenheit. The Kelvin scale is the absolute temperature scale used by scientists; it starts at absolute zero 0 K and has the same unit size as the Celsius scale. You can convert Celsius to Kelvin simply by adding 273.15.
Because 0 K is the lowest possible temperature, the Kelvin scale does not use the word "degrees" or have negative numbers!
Which subatomic particle has no charge?
EasyThe neutron is the subatomic particle that has no electrical charge (it is neutral). Neutrons are located in the nucleus of an atom alongside protons and have slightly more mass than a proton. They play a vital role in stabilizing the nucleus.
James Chadwick discovered the neutron in 1932, a discovery that was essential for the later development of nuclear fission and the atomic bomb!
What type of wave is a light wave?
MediumA light wave is a transverse electromagnetic wave. Unlike sound waves, which are longitudinal and require a medium, light waves consist of oscillating electric and magnetic fields that are perpendicular to each other and to the direction of travel.
Because light is an electromagnetic wave, it can travel through the total vacuum of space, which is how sunlight reaches us!
What type of energy is stored in a compressed spring?
EasyElastic Potential Energy is the energy stored in an object when it is temporarily deformed, such as when a spring is compressed or stretched. When the spring is released, this stored energy is converted back into kinetic energy (motion). The amount of energy stored depends on the spring's stiffness and how far it has been displaced.
This same type of energy is what allows a professional archer's bow to launch an arrow at speeds of over 200 mph!
What does a Prism do to white light?
MediumA prism disperses (splits) white light into its constituent colors-red, orange, yellow, green, blue, indigo, and violet. This happens because different colors of light travel at different speeds through the glass, causing them to refract (bend) at different angles.
Isaac Newton was the first to prove that the colors come from the light itself, not from the glass of the prism!
What is the power of a lens measured in?
HardThe power of a lens is measured in Dioptres (D). It is defined as the reciprocal of the focal length of the lens in meters P = 1/f. A convex (converging) lens has positive power, while a concave (diverging) lens has negative power.
If you have a prescription for "-2.50" glasses, it means you are using diverging lenses with a power of -2.5 dioptres!
Who is the father of the Modern Atomic Theory?
HardJohn Dalton is considered the "father of modern atomic theory." In the early 1800s, he proposed that all matter is composed of tiny, indivisible particles called atoms, that atoms of a given element are identical in mass and properties, and that chemical reactions involve the rearrangement of these atoms.
Dalton was also a pioneer in the study of color blindness, a condition he had himself, which was once known as "Daltonism" in his honor!
What type of circuit has only one path for current?
EasyA series circuit has only one path for the electric current to flow. This means that the same current passes through every component in the circuit. If one component fails or the path is broken, the entire circuit stops working.
Old-fashioned Christmas lights were often wired in series, so if one tiny bulb burnt out, the whole string would go dark!
What is the unit of force?
EasyThe Newton (symbol N) is the SI unit of force. It is defined as the amount of force needed to accelerate a one-kilogram mass at a rate of one meter per second squared 1 m/s^2. It was named after Sir Isaac Newton in recognition of his work on classical mechanics, particularly his second law of motion F=ma.
To get a physical feel for how much "one Newton" of force is, it is roughly equivalent to the weight of a small apple (about 100 grams) sitting in the palm of your hand. It's a fitting comparison, given the legend of Newton and the apple tree!