Ultrasonic waves cannot be heard by humans. They have frequencies higher than 20,000 Hz, beyond the range of human hearing. While some animals can detect ultrasonic frequencies, humans cannot perceive these waves audibly without the aid of specialized equipment.
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Food cooks faster in a pressure cooker because the high pressure inside increases the boiling point of water, raising the cooking temperature. This higher temperature accelerates the cooking process, reducing the time needed to cook the food.
A white and smooth surface is a poor absorber of heat and a good reflector. It reflects most of the incoming light and heat, minimizing absorption and thus remaining cooler.
When sealed biscuits are kept inside the refrigerator, they become crispy because the humidity inside the refrigerator is generally low, which helps absorb excess moisture from the biscuits. This drying effect restores their crispiness.
Water has a higher heat capacity compared to a piece of iron, gold, or benzene. This means water can absorb more heat before its temperature rises significantly, making it an effective coolant and thermal buffer.