Light Mirrors and Lenses Class 8 Long Question Answer

Light Mirrors and Lenses Class 8 Long Question Answer

Light Mirrors and Lenses Class 8 Long Question Answer

Question 1.

How does the appearance of an object change when viewed through a glass tumbler filled with water, and what causes this effect?

Answer:

When a pencil is viewed through a glass tumbler filled with water, it appears bent or displaced. This phenomenon occurs due to refraction, which is the bending of light as it passes from air into water. The change in speed of light in different media causes the visual distortion of the pencil's shape.

Question 2.

What are the characteristics of images formed by concave and convex mirrors, and how do they differ in practical applications?

Answer:

Concave mirrors produce real, inverted images that can be enlarged when the object is close, making them suitable for applications like shaving mirrors. In contrast, convex mirrors create virtual, erect images that are smaller, providing a wider field of view, which is why they are used in vehicle side mirrors and security surveillance.

Question 3.

Explain the law of reflection and its significance in understanding how mirrors work.

Answer:

The law of reflection states that the angle of incidence is equal to the angle of reflection. This principle is crucial for understanding how mirrors form images. When light strikes a mirror, it reflects at the same angle at which it arrives, allowing us to see clear images, as demonstrated in various mirror applications.

Examples from Real Life

Question 1.

Solar concentrators

Answer:

Real-life application: Solar power plants, like the Ivanpah Solar Electric Generating System in California, utilise thousands of mirrors (heliostats) that track the sun and focus its rays on a central tower. The heat produced can reach temperatures high enough to produce steam, which drives turbines to generate electricity. This technology is a crucial part of the shift towards renewable energy sources, showcasing how concave mirrors can play a significant role in sustainable energy solutions.

Question 2.

Safety and surveillance with convex mirrors

Answer:

Real-life application: In road safety, convex mirrors are installed at intersections and sharp bends to help drivers see oncoming traffic from both directions. This reduces the likelihood of accidents by providing better visibility. Similarly, in retail stores, convex mirrors are used to monitor large areas, helping to deter theft and ensure customer safety. Their unique ability to create erect, diminished images makes them invaluable in these contexts.

Question 3.

The human eye and vision correction

Answer:

Real-life application: Eye glasses and contact lenses are designed to correct vision by using convex or concave lenses, depending on whether a person is farsighted or nearsighted. For instance, convex lenses are used to help those who are farsighted by converging light. rays to focus them correctly on the retina. This application of lenses in eyeglasses is a direct use of the principles of optics discussed in the chapter, demonstrating how understanding light behaviour can enhance our quality of life.