Everyday Science

Carbon dating, also known as radiocarbon dating, uses the radioactive decay of carbon-14 to determine the age of organic materials from the prehistoric period. It is the most common method for dating archaeological and geological samples up to about 50,000 years old.

Vitamin B-9 is commonly known as folate, which is essential for DNA synthesis and cell growth. The other options correspond to different vitamins with distinct functions.

The audio signals of television are transmitted using frequency modulation (FM) because FM provides better noise immunity and sound quality compared to amplitude modulation (AM).

Common TV remote controls use infrared waves to transmit signals to the television. Infrared light is invisible to the human eye and is well-suited for short-range communication like remote controls.

1 meter is equal to 100 centimeters because the prefix 'centi-' means one hundredth, so 100 centimeters make up 1 meter.

All the options listed—Petrol, Kerosene, and Paraffin oil—are types of liquid fuels commonly used for combustion and energy purposes.

Carbohydrates are the body's primary and quickest source of energy because they are easily broken down into glucose, which cells use for fuel. Minerals and vitamins do not provide energy, and 'None of these' is incorrect.

The visible part of the ear is called the pinna, which is also referred to as the external ear. Therefore, both options A (External Ear) and B (Pinna) correctly describe the visible part of the ear, making option D (both A & B) the correct answer.

The Earth's atmosphere contains approximately 21% oxygen by volume, which is essential for respiration in most living organisms. This is a well-established scientific fact.

The iron needle floats on the water surface because of surface tension, which acts like a thin elastic sheet on the water surface preventing the needle from sinking if placed gently. The needle's density is greater than water, so density difference is not the reason.

Combustion requires oxygen to occur because oxygen supports the chemical reaction that releases heat and light. While air contains oxygen, it is the oxygen itself that is essential for combustion, not air as a whole.

Nitrogen is the main constituent of air by volume, making up about 78% of the Earth's atmosphere, which is more than any other gas including oxygen, hydrogen, or helium.

Soap is made by the saponification process, which involves boiling fats or oils with caustic soda (sodium hydroxide). This reaction produces soap and glycerine.

Microwaves are used for communication by artificial satellites because they can penetrate the atmosphere with minimal interference and support high data transmission rates, making them ideal for satellite communication.

Permanent hardness in water is caused by dissolved salts like calcium sulfate and magnesium sulfate, which do not get removed by boiling. Calcium sulfate is a common cause of permanent hardness.

A photostat machine works by creating an electrostatic image on a drum or plate, which is then developed with toner to produce a copy. This process is based on electrostatic principles, making option D correct.

Milk tastes sour when left open because bacteria convert lactose into lactic acid, which causes the sour taste.

Hydrology is the scientific study of the movement, distribution, and quality of water on Earth, which includes rainfall as a key component of the water cycle.

1 meter is equal to 1000 millimeters because 1 meter = 100 centimeters and 1 centimeter = 10 millimeters, so 100 × 10 = 1000 millimeters.

An adult typically has 32 permanent teeth, including wisdom teeth. This is the standard number in human dentition after all permanent teeth have erupted.

A rainbow is seen when sunlight is refracted, reflected, and dispersed by raindrops. To observe a rainbow, the observer must have their back to the Sun and face the raindrops where the light is being refracted.

Watermelon contains about 92-94% water, with most reliable sources citing approximately 92-93%. Among the given options, 93% is the most accurate and commonly accepted figure for watermelon water content.

A typical three-year-old child usually has a full set of 20 primary (baby) teeth. This is the standard number of deciduous teeth in young children before permanent teeth begin to erupt.

Mica is known for being a good conductor of heat while being an electrical insulator, meaning it does not conduct electricity well. This makes option D the correct answer.

The Earth is not a perfect sphere but an oblate spheroid, meaning it is slightly flattened at the poles and bulging at the equator due to its rotation.