Physics

Alpha rays consist of positively charged alpha particles (helium nuclei), making them positively charged particles emitted by radioactive elements. Beta rays are negatively charged electrons, and gamma rays are neutral electromagnetic radiation.

A moving object always possesses kinetic energy because kinetic energy is the energy associated with motion. Potential energy depends on position, thermal energy relates to heat, and magnetic energy depends on magnetic fields, so they are not always present in a moving object.

A definite area or space where a thermodynamic process takes place is called a thermodynamic system. The other options refer to different concepts: a thermodynamic cycle is a series of processes, a thermodynamic process is a change within the system, and thermodynamic laws govern these processes.

Francis William Aston invented the mass spectrograph, which allowed the measurement of isotopic masses and led to the discovery of isotopes. This invention was a significant advancement in mass spectrometry.

The speed of sound in water at 20 °C is approximately 1474 m/s, which is the most accurate value among the given options. Other values are either approximate or less precise.

In the cgs (centimeter-gram-second) system, surface tension is measured in dynes per centimeter (dyn/cm), which is the force per unit length. Pascal and N/m are SI units, not cgs units.

Galileo Galilei is credited with the idea of the law of inertia, which states that an object in motion stays in motion unless acted upon by an external force. This concept laid the foundation for Newton's first law of motion.

Refraction of sound occurs when sound waves pass from one medium to another or when there is a variation in temperature or density within a medium, causing the sound waves to bend. Since both water and air can cause such refraction, the correct answer is 'Both A & B'.

High-energy subatomic particles arriving from outer space are known as cosmic rays. They primarily consist of protons and atomic nuclei, but the term 'cosmic rays' specifically refers to these energetic particles from space.

Max Planck is famous for his discovery of energy quanta, which laid the foundation for quantum theory. He introduced the concept that energy is quantized, which is distinct from the photon concept introduced later by Einstein.