science & technology Online Quiz - 313

Sound is a mechanical wave that requires a medium (solid, liquid, or gas) to propagate and is not an electromagnetic wave. Light, radio waves, and X-rays are all electromagnetic waves that can travel through vacuum. Electromagnetic waves are oscillations of electric and magnetic fields, while sound is a pressure wave.

According to the law of reflection, the angle of incidence always equals the angle of reflection when measured from the normal (perpendicular line) to the mirror surface. This is a fundamental principle of geometric optics.

J.J. Thomson discovered the electron in 1897 through cathode ray tube experiments. He determined that cathode rays were negatively charged particles much smaller than atoms, which he called 'corpuscles' - later named electrons.

Galileo made multiple significant contributions: he developed the telescope for astronomical use (not invented it), discovered four of Jupiter's moons (Io, Europa, Ganymede, Callisto), and discovered pendulum isochronism. Option D 'All are correct' appropriately acknowledges all his achievements.

Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth. The term derives from the Greek 'seismos' (earthquake) and 'logia' (study of). Seismologists analyze seismic waves to understand Earth's internal structure.

Nokia was founded in Finland in 1865 as a paper mill and later became a telecommunications giant. Finland, not England, Auckland (which is in New Zealand), or Germany, is Nokia's country of origin. The company is synonymous with Finnish innovation in mobile technology.

Samsung Electronics is headquartered in Seoul, South Korea, and is the largest technology company in the country. It was founded in 1969 and has grown to become one of the world's largest electronics manufacturers. North Korea is a separate country with minimal industrial capacity, while South Africa and South America are geographical regions, not countries where Samsung originated.

Motorola was founded in the United States in 1928 by Paul and Joseph Galvin. The company was headquartered in Schaumburg, Illinois for decades before being split and sold to Google and Lenovo. It played a pioneering role in developing mobile phones and telecommunications equipment.

LG Electronics is a South Korean multinational electronics company headquartered in Seoul. It is part of LG Corporation, one of South Korea's largest chaebols (family-controlled conglomerates). LG was originally founded as GoldStar in 1958 and merged with Lucky Chemical to form Lucky-GoldStar, later abbreviated to LG.

All electromagnetic waves (X-rays, gamma rays, infrared, ultraviolet, and visible light) travel at the same speed in a vacuum - the speed of light (c ≈ 3×10^8 m/s). They are not all affected by magnetic fields, not all damaging to health, and they have very different wavelengths.

To solve this question, the user needs to know the basic principles of thermodynamics and the concept of heat transfer through radiation. When an object is heated, it emits thermal radiation in the form of electromagnetic waves. This radiation carries energy away from the object, causing it to cool down.

Now, let's go through each option and explain why it is right or wrong:

A. Electrons: This option is incorrect because the emission of electrons is not a form of heat transfer. Electrons are negatively charged particles that are involved in electrical conduction and chemical reactions, but they do not play a role in thermal radiation.

B. Radio waves: This option is incorrect because radio waves are a type of electromagnetic radiation, but they have a much lower frequency and longer wavelength than the type of radiation emitted by a hot object. Radio waves are typically used for communication and broadcasting, but they are not involved in heat transfer.

C. Visible light: This option is incorrect because visible light is also a type of electromagnetic radiation, but it has a much higher frequency and shorter wavelength than the type of radiation emitted by a hot object. Visible light is responsible for the colors we see, but it is not involved in thermal radiation.

D. Infra-red radiation: This option is correct. Infra-red radiation is a type of electromagnetic radiation that has a frequency lower than visible light but higher than radio waves. It is the type of radiation that is emitted by a hot object as it cools down. Infra-red radiation is responsible for the heat we feel when we stand near a hot object, such as a fire or a stove.

Therefore, the correct answer is: D. Infra-red radiation.

Lead is the best material for storing gamma radioactive substances because it has high density and atomic number, making it an excellent shield against gamma radiation. Graphite, aluminium, and glass offer minimal protection against gamma rays.

Using the formula Energy = Voltage × Charge, we can calculate Charge = Energy / Voltage = 10J / 2V = 5 Coulombs. The relationship E = VQ is fundamental in electrical circuits.

Electricity meters measure the total energy consumed by a household, typically in kilowatt-hours (kWh). This is then used to calculate the cost. They do not measure charge (coulombs), power (watts), or current (amps) directly - these are instantaneous values.

Using the linear scale formula: $T = \frac{L_x - L_{ice}}{L_{steam} - L_{ice}} \times 100$. Here, $\frac{50 - 20}{170 - 20} \times 100 = \frac{30}{150} \times 100 = 0.2 \times 100 = 20$. Thus, the temperature is 20 degrees Celsius.

In a cathode ray tube, the hot metal filament (cathode) emits electrons through a process called thermionic emission. These electrons are then accelerated toward the anode, forming the cathode ray. Protons and neutrons remain in the nucleus, and X-rays are produced when electrons strike the target, not emitted by the filament.

Using conservation of momentum: Initial momentum = (2kg × 3m/s) + (1kg × -4m/s) = 6 - 4 = 2 kg m/s. After collision, combined mass = 3kg moving with velocity v. So 3v = 2, giving v = 2/3 m/s. The negative sign for object B's velocity indicates opposite direction.

Dark animal fur is the best absorber of infrared radiation because dark colors absorb more radiation, while white or shiny surfaces reflect it. This is why animals in cold climates often have dark fur. White paper reflects, shiny metal is highly reflective, and window glass is transparent to most infrared.