Correct Answer: C

Rationale: Rainbows are formed due to the refraction and dispersion of sunlight by water droplets in the atmosphere. When sunlight enters a water droplet, it is refracted, then internally reflected, and finally refracted again as it exits the droplet. This dispersion of light into its component colors creates the beautiful rainbow we see in the sky. Choice A, diffraction, involves bending of light around obstacles or through narrow openings, not the splitting of light into colors as seen in rainbows. Choice B, interference, refers to the phenomenon where two or more light waves overlap and interact, producing a pattern of light and dark bands, which is not the case with rainbows. Choice D, reflection from clouds, does not accurately describe the process involved in the formation of rainbows through refraction and dispersion of light by water droplets.

Correct Answer: D

Rationale: The correct formula to calculate gravitational potential energy near the Earth's surface is Potential Energy = Mass Acceleration due to gravity Height. This formula considers the mass of the object, the specific acceleration due to gravity near the Earth's surface (approximately 9.81 m/s^2), and the vertical distance from the reference point. Choice A is incorrect as it does not include height in the formula. Choice B is incorrect as it involves force instead of acceleration due to gravity. Choice C is incorrect as it multiplies mass, height, and gravity, missing the actual acceleration due to gravity term.

Correct Answer: C

Rationale: Endospores are the correct answer. Endospores are dark, round structures observed within some bacterial cells. They are highly resistant dormant structures formed by certain bacteria in response to harsh environmental conditions. Ribosomes are not dark, round structures within bacterial cells; they are responsible for protein synthesis. Flagella are long, whip-like appendages used for movement and are not dark, round structures within bacterial cells. Capsules are outer layers of polysaccharides that some bacteria produce for protection and adherence, not dark, round structures within bacterial cells.

Correct Answer: D

Rationale: Constructive interference occurs when two identical waves are perfectly aligned and reinforce each other. This results in an increase in the overall amplitude of the wave. Refraction refers to the bending of waves as they pass from one medium to another, reflection is the bouncing back of waves when they encounter a boundary, and diffraction is the bending of waves around obstacles and openings. In this scenario, the waves are not changing direction or bending but rather combining to produce a wave with a larger amplitude, which is characteristic of constructive interference.

Correct Answer: C

Rationale: The human eye focuses light by adjusting the shape of its lens. The lens changes shape to allow the eye to focus on objects at different distances, a process known as accommodation. The cornea is the transparent outer covering of the eye that helps to focus light but does not change shape like the lens. The iris controls the size of the pupil to regulate the amount of light entering the eye. The retina is the light-sensitive layer at the back of the eye that receives and processes images but does not adjust the focus of light.