The question asks about the behavior of light when it encounters an opaque object. We need to understand the fundamental properties of opaque materials and how they interact with light.
Correct Option: B) It is absorbed by the object. Opaque objects are defined by their property of absorbing light, preventing its transmission. The light energy is converted into other forms, primarily heat, within the material.
The question asks about the property of light that explains its straight-line propagation. This phenomenon is often referred to as rectilinear propagation of light. We need to identify which fundamental nature or characteristic of light best describes this behavior.
C) Particle nature. The particle nature of light (photons) explains why it travels in straight lines, forming sharp shadows and following rectilinear paths in homogeneous media. This is the basis of ray optics.
The question asks to identify which phenomenon is NOT an example of rectilinear propagation of light. Rectilinear propagation means that light travels in straight lines in a uniform medium. We need to evaluate each option based on this principle.
Correct Option: B) Formation of rainbows
Rainbows are formed due to a combination of refraction, dispersion, and total internal reflection of light by water droplets. These processes involve light bending and splitting, which are not examples of simple rectilinear propagation. While light travels in straight lines between interactions with water droplets, the overall phenomenon relies on light deviating from its initial straight path.
This question asks about the behavior of light when it travels from one medium (air) to another (water). The key concept here is the refractive index of a medium, which dictates how light interacts with it, specifically its speed.
Correct Option: B) Decreases — When light passes from an optically rarer medium (air) to an optically denser medium (water), its speed decreases due to the higher refractive index of water.
The question asks to identify the optical phenomenon where light changes its direction when passing from one medium to another. We need to recall the definitions of the given options to find the correct one.
B) Refraction is the phenomenon where light changes its direction as it passes from one transparent medium to another. This change in direction is due to the change in the speed of light in different media.
The speed of light depends on the medium through which it travels. This speed is inversely related to the refractive index of the medium. We need to identify the medium with the lowest refractive index.
D) Vacuum — Light travels fastest in a vacuum because a vacuum has the lowest possible refractive index, which is 1. The speed of light in a vacuum is its maximum possible speed, approximately \(3 \times 10^8 \text{ m/s}\).