Physics Test - 2

The ozone layer is a layer in Earth 's atmosphere containing relatively high concentrations of ozone (O3). The ozone layer absorbs 97-99% of the Sun 's medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which potentially damages exposed life forms on Earth.

A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km. 

Newton 's first law of motion -sometimes referred to as the law of inertia-states that every object will remain at rest or in uniform  motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia.

Cathode rays are streams of electrons observed in vacuum tubes. When these rays encounter metal, they can cause the emission of various types of radiation.

• γ- rays: High-energy electromagnetic radiation, typically emitted from radioactive materials.
• X - rays: A form of electromagnetic radiation with high energy that can penetrate materials, often used in medical imaging.
• α- rays: Particles consisting of two protons and two neutrons, emitted from the nucleus of some radioactive atoms.
• β- rays: High-energy, high-speed electrons or positrons emitted by certain types of radioactive decay.

Among these, the most relevant emission when cathode rays strike metal is X - rays . This phenomenon occurs due to the interaction of the high-speed electrons with the metal atoms, resulting in the release of X - rays.

The sensation of hearing of any sound persists in our brain for 0.1s.This is called the persistence of hearing.

The cassette tape contains a magnetic strip wound around two spools. Tiny magnetic particles are randomly scattered throughout the tape. A tape recorder should not be kept near a magnet as the latter can cause the magnetic material to be pushed and pulled out of place. Rearranging the magnetic particles erases the sound. 

The Siemens is the unit of electric conductance, electric susceptance and electric admittance in the International System of Units (SI).

In the solid and liquid phase, water molecules are bonded to each other by virtue of an interaction between hydrogen atoms on one molecule and the oxygen atom of another —the process is referred to as "hydrogen bonding."The result is a kind of "skin "on liquid water 's surface.

The compressor is the motor (or engine) of the cooling system. It is normally at the bottom of the refrigerator in the back. The compressor runs whenever the refrigerator thermostat calls for cooling.

A mirage is a naturally occurring optical illusion or phenomenon in which light rays are bent due to refraction in layers of air of varying density. The image usually is upside down, enhancing the illusion that the sky image seen in the distance is really a water or oil puddle acting as a mirror.

Polished surfaces are poor radiators of heat. So loss of heat on that account is reduced and the electric iron remains hotter than otherwise.

When the length of a simple pendulum is halved, its period of oscillation changes significantly.

The period of a pendulum is influenced by its length, following the formula:

• The period (T) is proportional to the square root of the length (L): T ∝ √L .
• If the length is reduced to half (L/2), the new period can be calculated:

• The new period becomes T' = √(L/2) = (1/√2) * √L .
• This indicates that the new period is shorter than the original.

Thus, when the length is halved, the period of oscillation is decreased by a factor of √2 . This means the pendulum will swing back and forth more quickly than before.

The SI unit of intensity of illumination (illuminance) is the lux. An illuminance of 1.0 lux is produced by 1.0 lumen of light shining on an area of 1.0 m2.

An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer. Rectilinear propagation is a wave property which states that waves propagate (move or spread out) in straight lines. 

Pure water is a covalent compound. It exists as simple discrete molecules and have a simple molecular structure. Hence, it does not exist as ions. Therefore, pure water cannot conduct electricity due to the absence of mobile ions and electrons. One instance that water can conduct electricity is when there are dissolved substance in it. Only then will water dissociate into hydrogen ions and hydroxide  ions. The presence of mobile ions enables it to conduct electricity.

A gas pycnometer is a laboratory device used for measuring the density —or more accurately the volume —of solids, be they regularly shaped, porous or non-porous, monolithic, powdered, granular or in some way comminuted, employing some method of has displacement and the volume-pressure relationship known as Boyle 's Law. 

Lambert 's Law says that the intensity of emitted light from a surface is directly proportional to the cosine of the angle between the line of view and the normal to the surface. A Lambertian surface is a surface that follows this rule exactly. In practice, most surfaces are not perfectly Lambertian. A surface which obeys Lambert 's law is said to be Lambertian, and exhibits Lambertian reflectance. Such a surface has the same radiance when viewed from any angle.

The Surface tension pulls the surface of the drop equally at all points thus produces the spherical shape having the minimum surface area.

• Angular velocity is a vector amount portrayed as the progress of actual uprooting, which determines the  or rotational speed of an article and the pivot regarding which the item is turning.

• How much difference in precise molecule removal at a given timeframe is called Angular velocity. The track of the angular vector is vertical to the plane of a pivot, toward a path customarily demonstrated by the right-hand rule.

X-rays are part of the electromagnetic spectrum, an ionizing radiation with wavelengths shorter than ultraviolet light. X-ray tubes evolved from experimental Crookes tubes with which X-rays were first discovered in the late 19th century, and the availability of this controllable source of X-rays created the field of radiography, the imaging of opaque objects with penetrating radiation.