Every Day Science

Correct answer: 380–700 nm. Human eyes see wavelengths of about 380 nm (violet) to 700 nm (red).

Background: Visible light is a small part of the electromagnetic spectrum.

• 100–300 nm: 100–300 nm lies in the ultraviolet range.
• 500–900 nm: 500–900 nm extends into the infrared range.
• None of these: “None of these” is incorrect because 380–700 nm is correct.

Did you know? The colours are remembered as VIBGYOR.

Memory trick: 380 to 700 nm.

Correct answer: Satellite. A body that orbits a planet is called a satellite, either natural (like the Moon) or artificial.

Background: Artificial satellites are used for communication, weather, and navigation.

• Jet: A jet is an aircraft.
• Star: A star produces its own light and heat.
• Asteroid: An asteroid orbits the Sun, not a planet.

Did you know? The first artificial satellite was Sputnik 1 in 1957.

Memory trick: Orbits a planet = satellite.

Correct answer: Einstein. Albert Einstein proposed the theory of relativity (special in 1905, general in 1915).

Background: The theory changed our understanding of space, time, and gravity.

• Kepler: Kepler described the laws of planetary motion.
• Newton: Newton described the laws of motion and gravity.
• None of these: “None of these” is incorrect because Einstein is correct.

Did you know? Einstein won the Nobel Prize in 1921 for the photoelectric effect, not relativity.

Memory trick: Relativity → Einstein → E = mc².

Correct answer: 1, 2 and 3. Blood pressure depends on how narrow the vessels are, how strongly the ventricle pumps, and how much blood returns to the heart.

Background: Narrow vessels raise blood pressure, and wider vessels lower it.

• 1 only: Vessel diameter is only one of the factors.
• 3 only: Venous return is only one of the factors.
• 2, 3 only: Ventricle pressure and venous return are important, but vessel diameter also matters.

Did you know? Blood pressure is measured with a sphygmomanometer.

Memory trick: Vessels + pump + return = all three.

Correct answer: Displacement. Displacement is the shortest straight-line distance from the starting point to the final position, with a direction.

Background: Displacement is a vector, while distance is a scalar.

• Velocity: Velocity is the rate of change of displacement.
• Acceleration: Acceleration is the rate of change of velocity.
• Force: Force is a push or pull.

Did you know? If you return to the starting point, your displacement is zero.

Memory trick: Displacement = start to end, straight.

Correct answer: 120 torr. Normal systolic blood pressure is about 120 torr (mmHg).

Background: Systolic pressure is measured when the heart contracts.

• 80 torr: 80 torr is the normal diastolic pressure.
• 180 torr: 180 torr is dangerously high.
• 210 torr: 210 torr is dangerously high.

Did you know? Normal blood pressure is written as 120/80.

Memory trick: 120 over 80.

Correct answer: Dielectric heating. Microwave ovens heat food primarily through dielectric (dipolar) heating, where polar water molecules rotate rapidly in response to an alternating high-frequency electromagnetic field (2.45 GHz).

Background: While older guidebooks loosely referenced resonance, dielectric heating is the standard scientific explanation.

• Reflection: Metal walls reflect microwaves to keep them contained inside the cavity.
• Refraction: Refraction is the bending of waves passing through different media.
• Damped oscillation: Refers to oscillations that decay in amplitude over time.

Did you know? Percy Spencer discovered microwave cooking in 1945 when a chocolate bar melted in his pocket near an active radar magnetron.

Memory trick: Microwave heating = Dielectric (dipolar water rotation) heating.

Correct answer: EEG. An EEG (electroencephalogram) records the brain’s electrical activity.

Background: Electrodes are placed on the scalp.

• ECG: An ECG records the heart’s electrical activity.
• Lithotripsy: Lithotripsy breaks kidney stones with shock waves.
• None of these: “None of these” is incorrect because EEG is correct.

Did you know? EEG is used to diagnose conditions such as epilepsy.

Memory trick: E for Encephalon (brain); C for Cardio (heart).

Correct answer: 8 min 20 sec. Light travels about 150 million km at about 300,000 km/s, so sunlight takes about 8 minutes 20 seconds.

Background: The exact time varies slightly because Earth’s orbit is not a perfect circle.

• 3 min 7 sec: 3 min 7 sec is too short.
• 8 min 50 sec: 8 min 50 sec is slightly too long.
• None of these: “None of these” is incorrect because 8 min 20 sec is correct.

Did you know? Moonlight takes only about 1.3 seconds to reach Earth.

Memory trick: 8 min 20 sec.

Correct answer: Plastic. Plastic is amorphous: its particles are not arranged in a regular repeating pattern.

Background: Crystalline solids have a regular internal arrangement and sharp melting points.

• Salt: Salt is a crystalline solid.
• Sugar: Sugar is a crystalline solid.
• Ice: Ice is a crystalline solid.

Did you know? Glass is another well-known amorphous solid.

Memory trick: Crystals: salt, sugar, ice. Amorphous: plastic, glass.

Correct answer: Stem. The part of ginger we eat is a rhizome, an underground stem.

Background: Rhizomes have nodes and buds, which roots do not.

• Plant: Ginger is a plant, but the question asks which plant part it is.
• Leaf: Ginger is not a leaf.
• Root: Ginger is not a root, even though it grows underground.

Did you know? Turmeric is also a rhizome.

Memory trick: Ginger and turmeric = underground stems.

Correct answer: Parasites. Viruses are obligate parasites: they can multiply only inside living host cells.

Background: Outside a host cell a virus cannot reproduce.

• Predator: A predator hunts and eats other animals.
• Epiphyte: An epiphyte is a plant that grows on another plant without harming it.
• None of these: “None of these” is incorrect because parasites is correct.

Did you know? Antibiotics do not work against viruses; vaccines and antivirals are used instead.

Memory trick: Virus = parasite.

Correct answer: Mushrooms. Mushrooms are fungi. They lack chlorophyll and absorb food from decaying matter.

Background: Organisms that cannot make their own food are called heterotrophs.

• Algae: Algae contain chlorophyll and make food by photosynthesis.
• Grass: Grass makes its own food by photosynthesis.
• Tree: Trees make their own food by photosynthesis.

Did you know? Fungi play a key role in decomposing dead matter.

Memory trick: No chlorophyll → no food making.