HESI A2 Elsevier (HESI): HESI Admission Assessment - Set 5 - Part 3

Correct Answer: Particles vibrate parallel to wave travel

Longitudinal waves have particles that vibrate parallel to the direction of wave travel through the medium. Sound waves traveling through air illustrate this clearly by compressing and expanding the air along the path. Option a is incorrect because Longitudinal waves require a medium for propagation in most cases, especially for mechanical sound waves traveling through air. They do not travel only through a vacuum, unlike electromagnetic waves which can cross empty space. Option b is incorrect because Perpendicular electric and magnetic fields are features of electromagnetic waves, which are transverse rather than longitudinal in nature. Longitudinal waves are not defined by oscillating electromagnetic field components, so this description does not fit. Option c is incorrect because Sound is a primary example of a longitudinal wave traveling through a medium such as air. Saying longitudinal waves have no relationship with sound directly contradicts the most common example used in physi

Correct Answer: Frequency shift from relative motion

The Doppler effect is the apparent change in frequency observed when a wave source and observer move relative to each other through space. The motion causes higher or lower perceived pitch of sound. Option a is incorrect because Reflection from a curved mirror is described by the laws of reflection and the geometry of curved surfaces in optics. It does not involve any frequency change due to relative motion between source and observer. Option b is incorrect because Bending of light through a lens is refraction, which is governed by changes in the speed of light in different media. Refraction is not the same phenomenon as the Doppler effect, which involves motion. Option d is incorrect because The splitting of white light into its component colors is dispersion, which occurs when different wavelengths refract by different amounts. Dispersion happens through a prism or other transparent medium and is unrelated to motion.

Correct Answer: Reflection bounces, refraction bends

Reflection occurs when light bounces off a surface and returns into the original medium it came from. Refraction occurs when light bends as it passes from one medium into another due to a speed change. Option b is incorrect because Both reflection and refraction can occur in many different media in optics during normal interactions. They are not restricted to water or air alone, but happen at any boundary or surface where appropriate. Option c is incorrect because Reflection does not necessarily change the color of the light involved in the process during the optical event. Refraction is not defined by heat transfer at all, so both processes are about light direction. Option d is incorrect because Reflection and refraction are distinct optical phenomena that follow different physical laws in optics. Reflection is the bouncing of light off a surface back into the original medium, while refraction is the bending of light.

Correct Answer: Frequency up, wavelength down

When wave speed is constant during the propagation of a wave, frequency and wavelength are inversely related to each other. As frequency increases, the wavelength must decrease in proportion, and the reverse holds. Option a is incorrect because Frequency and wavelength do not increase together at constant wave speed in physics during wave propagation. Their product is the wave speed itself, so when speed stays constant for the wave, one quantity falls. Option c is incorrect because Frequency and wavelength cannot decrease together while wave speed remains constant during propagation. Their product equals the speed of the wave, so a decrease in both at the same time would lower wave speed. Option d is incorrect because Frequency and wavelength are tightly related through the wave speed of any wave in any medium during propagation. They are not independent quantities, especially when the speed of the wave is held constant.

Correct Answer: Slows down and bends toward normal

When light passes from air into water during refraction, it slows down because water is optically denser than air. This change in speed causes the light to bend toward the normal at the boundary. Option a is incorrect because Light slows down rather than speeding up when it enters a denser medium like water from air during refraction. Light also bends rather than continuing in a perfectly straight line through the boundary. Option b is incorrect because Light does not convert entirely into heat at the boundary between air and water during normal optical interactions. Some absorption occurs at the interface, but most of the light reflects, refracts, or transmits. Option c is incorrect because Light does not vanish at the air water surface during refraction at the boundary between media. Part of the incident light reflects back into the air at the boundary, while the remainder enters the water.

Correct Answer: Flow of charge through a conductor

Electric current is the flow of electric charge through a conductor in any circuit during operation. In metal wires the charge flow consists primarily of electrons drifting in response to an applied voltage. Option a is incorrect because Wire temperature relates to the thermal energy stored in the wire and to resistive heating during use, not to current. Current involves the actual movement of charge carriers rather than the heat content. Option b is incorrect because Gas pressure describes how strongly gas molecules push against the walls of any container holding the gas. It is unrelated to the electrical concept of moving charge through a conducting material in a circuit. Option d is incorrect because Light bending at a boundary between two media is refraction, which is an optical phenomenon governed by changes in light speed. It is not at all related to the flow of electric charge.

Correct Answer: Copper

Copper has many free electrons that move easily through its metal lattice, which makes it an excellent conductor of electricity. It is widely used in wiring throughout homes, electronic devices, and industrial machinery. Option b is incorrect because Rubber holds its electrons tightly in chemical bonds, which makes it a very poor conductor of electricity in any circuit. Rubber is widely used as an insulator around electrical wires to prevent electric shock. Option c is incorrect because Glass is an electrical insulator under ordinary conditions because its electrons are tightly bound within the chemical bonds of the silicate network. Glass does not allow electric current to flow through it easily. Option d is incorrect because Dry wood is a poor electrical conductor and behaves essentially like an insulator under ordinary conditions. Although moist wood may conduct somewhat due to dissolved ions in the water, dry wood resists current effectively.

Correct Answer: Moving charges create magnetic fields

Moving electric charges create magnetic fields around their path of motion through space. This relationship is the basis of electromagnets used in motors and devices, and it underlies the close connection between electricity and magnetism. Option a is incorrect because Magnetism and electricity coexist and are intimately related through electromagnetic theory in physics today. Moving charges generate magnetism in the space around their path, and changing magnetic fields can in turn generate electric currents. Option c is incorrect because Moving charges create magnetic fields rather than destroying them in any way at all. The interaction of moving charges with already existing magnetic fields can cause forces on the charges, but this never erases fields. Option d is incorrect because Magnetism does not prevent charges from moving in general at all in physics during electromagnetic interactions. Magnetism can exert forces on moving charges through the magnetic part of the Lorentz force,

Correct Answer: Opposition to flow of current

Resistance is the opposition to the flow of electric current in a conductor of any kind in an electrical circuit. Higher resistance reduces the current for a given applied voltage across the resistor. Option a is incorrect because Charge stored on a capacitor in a circuit relates to capacitance rather than to resistance in the circuit. Capacitance describes how much charge a component can hold per unit of voltage applied to it. Option b is incorrect because Voltage produced by a battery is the electromotive force of the battery, which is not the same as resistance in the circuit. Voltage drives current through the circuit, while resistance is the property opposing flow. Option c is incorrect because The mass of the conductor is unrelated to its resistance in any electrical circuit at all in physics. Resistance of a conductor depends on the material, the length, the cross sectional area, and the temperature.

Correct Answer: Unstable nucleus emits energy or particles

Radioactive decay occurs when an unstable atomic nucleus releases energy or particles to reach a more stable nuclear configuration. This nuclear process changes the identity or mass number of the original atom in many cases. Option a is incorrect because Radioactive decay is independent of temperature under normal conditions encountered in everyday life and laboratory settings. Heating a sample of radioactive material does not cause or significantly speed up the spontaneous nuclear changes. Option b is incorrect because Radioactive decay can release particles or various forms of radiation, but it does not always produce visible light. Many radioactive decays release invisible alpha or beta particles, or invisible gamma rays, rather than light. Option d is incorrect because Radioactive decay involves changes in the nucleus of the atom, not just changes in the electron arrangement around the nucleus. Modifying the electron arrangement creates ions or excited atoms, but those are not nucl