BZT1 - Physics: Waves and Optics

Explanation:

When light passes from one medium to another—such as from air to water—its speed changes because the optical density of the mediums differ. This change in speed causes the light to bend at the interface, a phenomenon known as refraction. Refraction is responsible for effects like a straw appearing bent in a glass of water.

Correct Answer:

Refraction

Why Other Options Are Wrong:

Reflection

Reflection is the bouncing back of light from a surface without a change in speed or medium.

Diffraction

Diffraction is the bending and spreading of light around obstacles or through narrow openings, not a speed change between media.

Dispersion

Dispersion occurs when white light separates into its component colors, as in a prism, due to different wavelengths refracting at slightly different angles, but it is not simply the speed change when entering another medium.

Explanation:

A convex mirror has a reflective surface that bulges outward, causing light rays to diverge and allowing a wider field of view. Security mirrors and vehicle side mirrors are classic examples of convex mirrors because they let observers see large areas. A makeup mirror is typically concave to magnify the face, so it is not convex.

Correct Answer:

B. Security mirror

Why Other Options Are Wrong:

A. Make up mirror

Makeup mirrors are usually concave to magnify images, not convex, which provides a smaller reflected image.

C. Side mirror of a car

Most side mirrors on vehicles are convex to give a wider view, but the question asks for a single best example; a security mirror is the most universally recognized convex application.

D. All of these are examples

Not all listed items are convex; the makeup mirror is typically concave, so this option is incorrect.

Explanation:

X-rays are a type of electromagnetic radiation with very short wavelengths, high frequencies, and high energy photons. They are ionizing, meaning they have enough energy to remove tightly bound electrons from atoms, which can cause chemical and biological effects. X-rays are composed of discrete packets of energy known as photons, and all these characteristics collectively define what an x-ray is.

Correct Answer:

All of the above

Why Other Options Are Wrong:

Very short wavelength electromagnetic radiation

While true, this description alone does not capture their ionizing nature or their particle-like photon characteristics, making it incomplete.

Ionizing radiation

X-rays are ionizing, but this option does not indicate that they are electromagnetic waves with very short wavelengths or that they consist of photons.

Packets of energy called photons

X-rays are indeed photons, but this alone does not describe their high energy, short wavelength, or ionizing capability.

Explanation:

Waves are traveling disturbances that propagate energy through a medium (mechanical waves) or through space (electromagnetic waves) without the bulk movement of matter. They can involve oscillations of particles, such as in water or sound waves, or oscillations of electric and magnetic fields, such as in light. Waves transmit energy from one point to another while the medium itself does not experience net displacement over long distances.

Correct Answer:

travelling disturbances

Why Other Options Are Wrong:

electromagnetic light

Light is one type of wave (electromagnetic), but this option is too narrow. Waves include mechanical waves, water waves, sound waves, and more, so defining waves only as light is incorrect.

sunlight and ocean waves

This mixes specific examples rather than giving a general definition. Waves are a broader concept encompassing many types beyond sunlight and water waves.

when somebody throws a rock at you

This describes an event, not a physical phenomenon. A rock being thrown is not a wave, although it may generate waves in a medium upon impact.

oscillations

Oscillations describe a periodic motion, but waves specifically involve the propagation of disturbances through space or a medium, which is more than just oscillation. Oscillations alone do not necessarily constitute a wave.

Explanation:

The law of reflection states that the angle of incidence equals the angle of reflection. Both angles are measured relative to the normal, which is an imaginary line perpendicular to the surface at the point where the light ray strikes. This relationship holds for all types of reflective surfaces, whether smooth like a mirror or irregular, ensuring that the direction of the reflected ray can be accurately predicted when the incident angle is known.

Correct Answer:

The angle of incidence equals the angle of reflection.

Why Other Options Are Wrong:

The angle of incidence is always greater than the angle of reflection.

This is incorrect because it contradicts the fundamental law of reflection. There is no physical principle that causes the incident angle to exceed the reflected angle consistently.

The angle of incidence is half of the angle of reflection.

Halving the incident angle has no basis in the behavior of light. Such a relationship would violate the predictable symmetry observed in experiments and theoretical optics.

The angle of incidence has no effect on the angle of reflection.

This is false because the reflected angle directly depends on the incident angle. If the incident angle changes, the reflection angle changes in exactly the same way, maintaining equality between the two.

Explanation:

Violet light has the shortest wavelength in the visible spectrum because it also has the highest frequency and therefore the highest energy of visible light. According to the relationship λ = c/f, where λ is wavelength, c is the speed of light, and f is frequency, higher frequency means shorter wavelength. Violet light’s higher energy photons correspond to this shorter wavelength compared to other visible colors.

Correct Answer:

Because it has the highest energy and frequency

Why Other Options Are Wrong:

Because it is the first color in the spectrum

The order of colors in a spectrum (often remembered as ROYGBIV) is a descriptive sequence and does not dictate wavelength. Being “first” is arbitrary and unrelated to wavelength length.

Because it is the least visible to the human eye

Human eye sensitivity does not determine the physical wavelength of light. While the eye may perceive violet less intensely than green, visibility is not the reason for its short wavelength.

Because it refracts the least in a prism

Violet light actually refracts the most in a prism because it has the shortest wavelength and higher frequency, which cause greater bending in dispersion. Therefore this statement is factually incorrect.

Explanation:

James Clerk Maxwell’s greatest contribution was unifying electricity, magnetism, and light into a single comprehensive theory. His set of equations, known as Maxwell’s equations, mathematically described how electric and magnetic fields interact and propagate as electromagnetic waves. This work demonstrated that light itself is an electromagnetic wave, providing the foundation for modern physics and technologies such as wireless communication and optics.

Correct Answer:

He unified electricity, magnetism, and light into a single theory.

Why Other Options Are Wrong:

He developed the theory of relativity.

The theory of relativity was developed by Albert Einstein, not Maxwell. While Maxwell’s equations influenced Einstein’s work, relativity is a distinct framework describing the relationship between space, time, and gravity.

He formulated the laws of motion.

The laws of motion were formulated by Sir Isaac Newton, centuries before Maxwell’s research. Maxwell’s contributions focus on electromagnetic phenomena, not classical mechanics.

He discovered the electron.

The electron was discovered by J.J. Thomson in 1897, long after Maxwell’s time. Although Maxwell’s theory laid the groundwork for understanding electromagnetic fields where electrons play a role, he did not discover the particle itself.

Explanation:

A convex mirror curves outward, causing reflected light rays to diverge and producing a virtual image that is smaller than the actual object but covers a wider field of view. This allows drivers to see more of the road behind them, reducing blind spots and improving situational awareness. However, because the images are smaller, objects appear farther away than they really are, so drivers must be cautious when judging distances.

Correct Answer:

The convex mirror provides a smaller, wider view, improving situational awareness

Why Other Options Are Wrong:

The convex mirror shows a larger image, making it harder to judge distances

A convex mirror produces a smaller, not larger, image, so this statement is inaccurate.

The flat mirror shows a distorted image, leading to confusion

A flat (plane) mirror provides an undistorted image of the same size as the object, so this description is incorrect.

The flat mirror provides a wider view but at a greater distance

A flat mirror does not provide a wider field of view than a convex mirror and does not change the perceived distance beyond normal reflection.

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.