General Physics

Since mercury is 13+ times as dense as water, a given volume of mercury would carry about 4.4 times as much heat, so mercury is best conductor of heat among the given options. It is the only metal that is liquid at standard conditions for temperature and pressure. Mercury has one of the narrowest ranges of its liquid state of any metal.

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Electron microscopes are used to observe a wide range of biological and inorganic specimens including microorganisms, cells, large molecules, biopsy samples, metals, and crystals. An electron microscope uses a beam of electrons to illuminate a specimen and produce a magnified image. An electron microscope (EM) has greater resolving power than a light-powered optical microscope because electrons have wavelengths about 100,000 times shorter than visible light photons.

The Milky Way is a barred spiral galaxy 100,000– 120,000 light-years in diameter containing 200–400 billion stars. It may contain at least as many planets, with an estimated 10 billion of those orbiting in the habitable zone of their parent stars. The Milky Way is the galaxy that contains our Solar System.

A cricketer lowers his hands while taking a catch to decrease the rate of momentum. Cricketers increase the time by pulling their hand’s backward with the ball while taking a catch. Linear momentum or translational momentum is the product of the mass and velocity of an object.

It is widely accepted that the first prototype of an electron microscope was built by Ernst Ruska and Max Knoll in 1931; it was not more powerful than an optical microscope, but it demonstrated the principle that is still used in today’s sophisticated and powerful instruments, and earned its builders a share of a Nobel Prize.

Basically, refrigeration system consists of devices that compress and expand refrigerant gas . When refrigerant gas is compressed it expels heat and when it is suddenly expanded, absorbs heat. A refrigerator (colloquially fridge) is a common household appliance that consists of a thermally insulated compartment and a heat pump (mechanical, electronic, or chemical) that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room.

Glass transmits visible light but blocks infrared thermal radiation from escaping. This amplifies the heat trapping effect. A solar cooker, or solar oven, is a device which uses the energy of direct sunlight to heat food or drink to cook it or sterilize it.

Longitudinal waves cannot travel through vacuum because such wave requires a medium such as solid liquid or air to travel through. They cannot travel through vacuum or in space. Longitudinal waves, also known as “l-waves”, are waves that have the same direction of vibration as their direction of travel, which means that the movement of the medium is in the same direction as, or the opposite direction to, the motion of the wave.

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