BZT1 - Physics: Waves and Optics

Explanation:

A converging lens, also called a convex lens, is thicker at the center and thinner at the edges. This shape causes parallel rays of light to bend toward a common point on the principal axis called the focal point. The focal point for a converging lens is considered positive because it is on the side where light rays converge after passing through the lens. This combination of shape and positive focal length is what allows convex lenses to focus light.

Correct Answer:

the focal point is positive and the lens is thinner at the edges and thicker at the center.

Why Other Options Are Wrong:

the focal point is positive and the lens is thicker at the edges and thinner in the center.

This describes a diverging (concave) lens, not a converging lens. In such a lens, light rays spread apart, and the focal point is considered negative.

the focal point is negative and the lens is thicker at the edges and thinner at the center.

While the thickness pattern matches a diverging lens, the focal point for a converging lens is positive. This option confuses the lens type and focal sign.

Explanation:

Gamma rays have extremely high energy and very short wavelengths, making them strongly ionizing. They can remove tightly bound electrons from atoms, breaking chemical bonds and damaging DNA, which can lead to mutations and cell death. While microwaves and visible light can cause some effects like heating or photochemical reactions, they lack the energy to ionize atoms. Radio waves have even lower energy and are generally not harmful at typical exposure levels.

Correct Answer:

Gamma rays, because they are a form of ionizing radiation with high energy.

Why Other Options Are Wrong:

Radio waves, because they have the longest wavelength.

Long wavelength corresponds to low energy, which is insufficient to ionize or damage cellular molecules significantly.

Microwaves, because they can heat tissues.

Although microwaves can cause heating, they are non-ionizing and generally do not directly damage DNA at normal exposure levels.

Visible light, because it can cause photochemical reactions.

Visible light is non-ionizing and lacks the energy required to break chemical bonds in DNA or cause direct ionization, limiting its ability to cause significant cellular damage compared to gamma rays.

Explanation:

In an electromagnetic wave, the electric field, magnetic field, and the direction of wave propagation are all mutually perpendicular. The electric field oscillates in one direction, the magnetic field oscillates in a direction perpendicular to the electric field, and the wave travels in a direction perpendicular to both fields. This orthogonal relationship allows electromagnetic waves to propagate through space at the speed of light, as described by Maxwell’s equations.

Correct Answer:

All of these: the three vectors are mutually perpendicular.

Why Other Options Are Wrong:

The velocity of the wave is perpendicular to the electric field and the magnetic field.

While true, this statement describes only part of the relationship. It omits that the electric and magnetic fields are also perpendicular to each other, making it incomplete.

The electric field is perpendicular to the magnetic field.

Although correct, this answer alone does not fully capture the three-way perpendicularity that includes the direction of wave propagation.

The magnetic field is perpendicular to the velocity of the wave.

This is accurate but partial, as it fails to mention the electric field’s perpendicularity, which is essential to describe the complete geometry of electromagnetic waves.

Explanation:

For a surface to function as a mirror, light rays must reflect at consistent angles according to the law of reflection. A smooth surface provides a uniform plane so that parallel rays reflect in a uniform, predictable direction, creating regular reflection. A rough or uneven surface has microscopic bumps and valleys, causing the incident light rays to reflect in many directions, producing diffuse reflection and destroying a clear image.

Correct Answer:

A smooth surface allows for regular reflection, while a rough surface scatters light, leading to diffuse reflection.

Why Other Options Are Wrong:

A smooth surface allows for diffuse reflection, while a rough surface creates regular reflection.

This reverses the actual phenomena. Smooth surfaces create regular reflection, not diffuse reflection.

Both smooth and rough surfaces produce regular reflection.

Rough surfaces scatter light in many directions and cannot maintain the parallel reflected rays needed for a regular reflected image.

Surface texture has no effect on the quality of reflection.

Surface texture is crucial; irregularities directly disrupt the uniform angles of reflection required for a mirror-like image.

Explanation:

In a transverse wave, particles of the medium oscillate perpendicular to the direction of wave propagation. The highest point is called the crest, while the lowest point is called the trough. Compressions and rarefactions are terms specific to longitudinal waves, where particles move parallel to the wave direction. Identifying the trough is essential for calculating properties such as amplitude, wavelength, and energy of transverse waves.

Correct Answer:

trough

Why Other Options Are Wrong:

crest

The crest is the peak or highest point of a transverse wave, opposite to the trough. Selecting this would incorrectly identify the wave’s minimum point as the maximum.

compression

Compression refers to areas of high particle density in longitudinal waves, not transverse waves. It does not describe the lowest point in a transverse wave.

rarefaction

Rarefaction refers to areas of low particle density in longitudinal waves. It is unrelated to the vertical displacement in transverse waves and does not correspond to the trough.

Explanation:

Converging lenses, also known as convex lenses, bend incoming parallel light rays toward a focal point on the opposite side of the lens, forming real or virtual images depending on object placement. Diverging lenses, or concave lenses, bend incoming parallel light rays outward, causing them to spread apart and appear to originate from a virtual focal point on the same side as the light source. This fundamental difference in light behavior determines the type and orientation of images each lens can produce.

Correct Answer:

Converging lenses bring light rays together, while diverging lenses spread them apart.

Why Other Options Are Wrong:

Converging lenses spread light rays apart, while diverging lenses bring them together.

This is the opposite of reality. Converging lenses focus light to a point, while diverging lenses cause light to spread out.

Both types of lenses bring light rays together but at different angles.

This is incorrect because only converging lenses bring rays together. Diverging lenses do not converge light at all—they spread it apart.

Converging lenses only work with visible light, while diverging lenses work with all types of electromagnetic radiation.

This is misleading and false. Both lens types can refract any electromagnetic wave capable of being refracted, not just visible light. The distinction between converging and diverging lenses is based on shape and light behavior, not wavelength.

Explanation:

Infrared radiation lies just below visible light in frequency on the electromagnetic spectrum. From highest to lowest frequency, the main regions are gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves, and radio waves. Counting downward from the highest frequencies, infrared is the fourth major region. It has a lower frequency than visible light but a higher frequency than microwaves, which places it fourth in this standard ordering.

Correct Answer:

Fourth

Why Other Options Are Wrong:

First

First would correspond to the highest-frequency region such as gamma rays, which have far greater frequency than infrared radiation. Infrared occupies a much lower place on the spectrum.

Second

Second typically aligns with X-rays or ultraviolet in terms of decreasing frequency, both of which are above visible and infrared. Infrared is therefore farther down the sequence than second.

Third

Third generally refers to visible light when ordering by decreasing frequency. Infrared is immediately below visible light, making third inaccurate for infrared’s position.

Explanation:

James Clerk Maxwell predicted the existence of electromagnetic waves mathematically in the 1860s, but he did not experimentally prove them. The first experimental demonstration of radio waves was carried out by Heinrich Hertz between 1886 and 1888, with 1887 recognized as the key year of his successful experiments showing that these waves behaved like light. He generated and detected radio waves, confirming Maxwell’s theory of electromagnetism.

Correct Answer:

Henrich Hertz, 1877

Why Other Options Are Wrong:

James Clerk Maxwell, 1865

Maxwell formulated the theoretical foundations of electromagnetism and predicted radio waves mathematically, but he did not conduct experiments to physically demonstrate their existence.

Nikola Tesla, 1893

Tesla made significant contributions to radio technology and wireless transmission but came after Hertz’s experiments. He helped develop practical radio communication rather than proving the fundamental existence of radio waves.

Guglielmo Marconi, 1901

Marconi is famous for pioneering long-distance radio communication and sending signals across the Atlantic, but this was decades after Hertz’s experimental verification.

Explanation:

In optics, a mirror is defined as any surface that is smooth enough to produce a regular reflection of light. When light rays strike a smooth surface, they reflect at equal angles, allowing the formation of clear images. The key aspect of a mirror is the ability to provide a specular reflection, not the ability to refract or magnify light.

Correct Answer:

Any surface that is smooth enough to produce a regular reflection

Why Other Options Are Wrong:

A surface that absorbs light and produces no reflection

A surface that absorbs light without reflecting it is the opposite of a mirror. Mirrors are specifically designed to reflect light, whereas an absorbing surface would prevent image formation. Materials like matte black paint absorb light and therefore cannot function as mirrors.

A device that refracts light to create images

Refraction involves the bending of light as it passes from one medium to another with different optical densities. Mirrors do not rely on refraction to produce images; they depend on reflection. Lenses, not mirrors, are used for refraction-based imaging.

A type of lens used to magnify objects

A lens is a transparent optical component that bends light to focus or magnify images. Mirrors do not magnify by bending light through a medium; instead, they reflect light from their surface. Although some curved mirrors can enlarge images, they do so by reflection, not by acting as lenses.