Physics

Internal friction in a fluid is known as viscosity, which measures the fluid's resistance to flow. Surface tension, resistance, and cohesive force are different physical properties and do not describe internal friction.

Materials whose atoms can be split are called fissionable materials because they can undergo nuclear fission, where the nucleus splits into smaller parts. Fusionable refers to materials that can undergo fusion, combustible relates to burning, and 'None of these' is incorrect.

Magnetism is a force that can attract or repel magnetic materials. Heat and light are forms of energy, and 'Kinetic' is an adjective related to motion, not a force itself.

When sound waves pass from air to water, their frequency remains unchanged because frequency depends on the source of the sound and does not change when the medium changes. However, speed and wavelength change due to different properties of the media, and intensity can also vary due to absorption and reflection.

The speed of sound in air at room temperature (around 20 °C or 68 °F) is approximately 343 meters per second, which converts to about 767 miles per hour. The given options are 1257 mph, 755 mph, 330 mph, and None of these. Since 330 mph is significantly lower than the actual speed and 755 mph is close but still slightly off, the best accurate choice is "None of these". Therefore, option D is correct. The original explanation was incorrect because it confused meters per second with miles per hour and gave an inaccurate conversion.

A hydrogen bomb operates on the principle of nuclear fusion, where light atomic nuclei combine to form heavier nuclei, releasing enormous energy. This distinguishes it from atomic bombs, which rely on nuclear fission.

The distance between the optical center of a convex lens and its principal focus is defined as the focal length. This is a fundamental property of lenses that determines their converging power.

A convex mirror always forms a virtual, diminished, and upright image regardless of the object's position. It never forms a real or inverted image, and the image is smaller rather than larger.

The M.K.S. system (Meter-Kilogram-Second) was introduced by Giovanni Giorgi, who proposed this system as a practical set of units for scientific measurements. The other options are unrelated to the introduction of the M.K.S. system.

A dioptre is the unit of measurement for the optical power of a lens, which is the reciprocal of its focal length measured in meters. Therefore, it directly relates to focal length, not the lens itself as a general object.

A wattmeter is specifically designed to measure the power in an electric circuit, which is the rate at which electrical energy is consumed or produced. The other instruments listed measure different quantities: a wavemeter measures frequency, and a viscometer measures viscosity.

Electromagnetism is a branch of physics that studies the interaction between electric and magnetic fields. It is not a branch of chemistry, so the correct answer is Physics.

Potential difference is defined as the work done in moving a unit charge between two points in an electric circuit, which matches the given definition exactly.

Robert Millikan determined the absolute value of the electron's charge through his oil drop experiment, which measured the charge on tiny charged droplets, allowing calculation of the electron's charge magnitude.

The neutron was discovered late because it carries no electric charge, making it difficult to detect using methods that rely on electric or magnetic fields. Its neutral charge meant it did not respond to electromagnetic detection techniques used for charged particles like protons and electrons.

One Coulomb is the charge of approximately 6.25×10^18 elementary charges (electrons). This is calculated by dividing 1 Coulomb by the charge of one electron (1.6×10^-19 C).

Very High Frequency (VHF) waves have shorter wavelengths compared to lower frequency waves. As frequency increases, wavelength decreases, so VHF waves have shorter wavelengths than lower frequency bands.

Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction, which is exactly described in option A. The other options describe unrelated physical concepts.

Mach number is the ratio of an object's speed to the speed of sound in the surrounding medium. Therefore, it is directly related to the speed of sound, not specifically to aircraft, ships, or light.

Aerodynamics is the branch of physics that studies the forces acting on bodies in motion through the air, such as lift and drag. This makes option C the correct answer.

The SI unit of luminous intensity, which measures the perceived power of light, is the candela. Watt is a unit of power, Pascal is a unit of pressure, and Joule is a unit of energy, so they are incorrect in this context.

Gamma rays consist of high-energy photons with very short wavelengths, making them the strongest photons among the options listed. X-rays also have strong photons but are generally less energetic than gamma rays. Microwaves have much lower photon energy, and 'Electromagnetic' is a broad category, not a specific radiation type.

The visible spectrum of light ranges approximately from 3900 to 7600 angstroms (Å), which corresponds to wavelengths visible to the human eye. Options A and C fall outside this range, making B the correct choice.

The gravitational acceleration on Earth is approximately 9.80 m/s², which is the standard value used in physics for calculations involving Earth's gravity.

Side view mirrors of vehicles are convex mirrors because they provide a wider field of view, allowing drivers to see more area behind and to the side of the vehicle, which enhances safety.