Noise & Radiation — Set 4

Correct Answer: B. Becquerel

The Becquerel (Bq) is the international unit used to measure the rate of radioactive decay. It is named after Henri Becquerel, who discovered radioactivity in 1896. This unit helps in quantifying the strength of a radioactive source.

Correct Answer: B. Galactic Cosmic Rays

Space is filled with high-energy protons and heavy ions known as galactic cosmic rays. Outside the Earth's magnetic field, astronauts are exposed to much higher doses of this ionizing radiation. Shielding spacecraft against these rays is a major challenge for Mars missions.

Correct Answer: A. An object breaking the sound barrier

A sonic boom is a loud, explosive noise caused by shock waves from an aircraft traveling faster than sound. It creates a sudden change in pressure that sounds like a loud bang. Generally, supersonic flights are restricted over land to prevent disturbance and structural damage.

Correct Answer: B. Iodine-131

Iodine-131 is absorbed by the thyroid gland and its radiation helps in destroying overactive or cancerous cells. This is a common application of targeted internal radiotherapy. It has a relatively short half-life of about 8 days.

Correct Answer: C. 140 dB

Sound at 140 dB causes immediate physical pain and can burst the eardrum. It is 10,000 times more intense than noise at 100 dB because the scale is logarithmic. Immediate protective measures are required at these extreme levels.

Correct Answer: B. Radio waves

Microwaves are a form of electromagnetic radiation with wavelengths between radio waves and infrared. They work by causing water molecules in food to vibrate, producing heat. They are non-ionizing and do not make the food radioactive.

Correct Answer: B. It remains radioactive for thousands of years

The correct answer is 'It remains radioactive for thousands of years'. Nuclear waste contains isotopes with extremely long half-lives that can stay dangerous for millennia. Storing this waste safely without leaking into groundwater is a massive engineering challenge. Most countries plan to use deep geological repositories for long-term disposal.

Correct Answer: B. Rustling leaves

Rustling leaves are generally measured at about 10-20 dB, very close to the threshold of hearing. 0 dB does not mean 'no sound', but rather the quietest sound a healthy human ear can detect. Silence in a vacuum would be truly zero energy, but in air, there is always some noise.

Correct Answer: A. Half of its atoms to decay

Half-life is a constant value for each specific radioactive isotope. It allows scientists to predict how long a material will remain active and dangerous. Generally, after 10 half-lives, the radioactivity drops to about 0.1% of the original.

Correct Answer: B. Green

Green light is globally accepted as the signal to proceed. In noise pollution mascot imagery, the guard Bholu often holds a green lantern to symbolize safety and ethical service. This color is chosen for its high visibility and distinctiveness from the red 'stop' signal.