Physics Basics — Set 2

Correct Answer: C. Albert Einstein

• **Albert Einstein** = Albert Einstein developed both the special theory (1905) and the general theory (1915) of relativity. • **E=mc²** — His mass-energy equivalence formula E=mc² showed that mass and energy are interconvertible. • 💡 Wrong-option analysis: Max Planck: proposed quantum theory and Planck's constant; Niels Bohr: proposed the atomic model with quantized electron orbits; Michael Faraday: discovered electromagnetic induction and laws of electrolysis.

Correct Answer: C. Wind speed

• **Wind speed** = An anemometer is a common weather station instrument used to measure the speed of wind. • **RPM** — Cup anemometers spin faster as wind speed increases, and their rotation per minute is converted to wind speed. • 💡 Wrong-option analysis: Humidity: is measured by a hygrometer; Solar radiation: is measured by a pyrheliometer; Water depth: is measured by a fathometer or sonar.

Correct Answer: A. 10^-9

• **10^-9** = The prefix 'nano' denotes a factor of 10 to the power of negative nine (one-billionth). • **1 nm** — One nanometer = 10^-9 meters, commonly used to describe wavelengths of light and atomic scales. • 💡 Wrong-option analysis: 10^-12: is the prefix 'pico', not nano; 10^-3: is the prefix 'milli'; 10^-6: is the prefix 'micro'.

Correct Answer: D. J.J. Thomson

• **J.J. Thomson** = J.J. Thomson discovered the electron in 1897 through cathode ray tube experiments, proving atoms are not indivisible. • **1906** — Thomson received the Nobel Prize in Physics in 1906 for his discovery of the electron. • 💡 Wrong-option analysis: James Chadwick: discovered the neutron in 1932; Enrico Fermi: pioneered nuclear reactor technology; John Dalton: proposed the atomic theory but did not discover subatomic particles.

Correct Answer: D. Pascal

• **Pascal** = The Pascal is the SI unit of pressure, named after the scientist Blaise Pascal. • **1 N/m²** — One Pascal equals one Newton per square meter (N/m²), making it a derived unit. • 💡 Wrong-option analysis: Henry: is the SI unit of electrical inductance; Joule: is the SI unit of energy and work; Newton: is the SI unit of force, not pressure.

Correct Answer: B. James Watt

• **James Watt** = James Watt significantly improved the steam engine by adding a separate condenser in 1765, greatly increasing efficiency. • **1765** — The separate condenser prevented energy waste by keeping the cylinder always hot, patented in 1769. • 💡 Wrong-option analysis: Thomas Newcomen: built the earlier steam engine (1712) but without a separate condenser; George Stephenson: developed the steam locomotive, not the condenser improvement; Robert Fulton: applied steam power to boats, did not invent the improved steam engine.

Correct Answer: A. Frequency

• **Frequency** = Hertz is the SI unit of frequency, defined as one complete cycle per second. • **1 Hz = 1 cycle/second** — Named after Heinrich Hertz, who experimentally proved the existence of electromagnetic waves. • 💡 Wrong-option analysis: Force: is measured in Newton; Energy: is measured in Joule; Power: is measured in Watt.

Correct Answer: C. Lactometer

• **Lactometer** = A lactometer is a specialized hydrometer used to check the purity of milk by measuring its specific gravity. • **Archimedes' principle** — A lactometer works on the principle of buoyancy; pure milk sinks to a specific depth. • 💡 Wrong-option analysis: Saccharometer: measures sugar content in a liquid; Hydrometer: measures relative density of liquids in general; Galvanometer: detects and measures small electric currents.

Correct Answer: D. Galileo Galilei

• **Galileo Galilei** = Galileo Galilei is called the father of experimental physics for his use of systematic observation and experiment to test physical laws. • **inclined plane** — His famous inclined plane experiments disproved Aristotle's claim that heavier objects fall faster. • 💡 Wrong-option analysis: Richard Feynman: was a 20th-century physicist known for quantum electrodynamics; Aristotle: relied on pure logic rather than controlled experiments; Stephen Hawking: worked on theoretical cosmology and black holes, not experimental physics.

Correct Answer: B. 3 x 10^8 m/s

• **3 x 10^8 m/s** = The speed of light in a vacuum is approximately 3 × 10⁸ meters per second (exactly 299,792,458 m/s). • **c** — Denoted by 'c', this is the maximum speed at which any matter or information can travel in the universe. • 💡 Wrong-option analysis: 3 x 10^6 m/s: is 100 times too slow; 3 x 10^5 m/s: is 1,000 times too slow — this is actually the approximate speed of sound in a very different context; 3 x 10^10 m/s: is 100 times too fast, exceeding even the actual speed of light.