Chapter 15- Light Class 7 science- Extra Question and Answers

Chapter 15- Light -Question and Answers -Solved Worksheet

Question-Why is the candle flame not visible when looking through the bent pipe in the experiment?
Answer- The candle flame is not visible through the bent pipe because it demonstrates that light travels in a straight line. The bend in the pipe obstructs this straight path, preventing the light from reaching the observer’s eye.

Question-What type of image is formed when light rays from an object reflect off a flat mirror?
Answer- A flat (plane) mirror forms a virtual image. This occurs because the light rays appear to diverge from a point behind the mirror, creating an image that seems to be behind the mirror but cannot be projected on a screen.

Also Check – What is Light? An Easy-to-Understand Guide

Question-Why does a rough or dark-coloured surface absorb more light than it reflects?
Answer- A rough or dark-coloured surface absorbs more light due to its texture and colour, which prevents efficient reflection of light rays. The absorbed light often converts to heat, resulting in less light being reflected back.

Question-How does the nature of a surface affect the behaviour of light, specifically in terms of reflection and transmission?
Answer- The nature of a surface determines whether light is reflected, absorbed, or transmitted. Shiny surfaces like mirrors reflect most of the light, while transparent materials like glass transmit it. Rough or opaque surfaces tend to absorb light.

Question-What distinguishes a real image from a virtual image in terms of light rays?
Answer- A real image is formed by the actual convergence of light rays at a point, and it can be projected on a screen. A virtual image, however, is formed by the apparent convergence of diverging light rays and cannot be projected.

Question-What determines the path of a reflected ray after it strikes a surface?
Answer- The path of the reflected ray is determined by the nature of the surface (whether it’s smooth or rough) and the angle of incidence. The smoother the surface, the more defined the path of the reflected ray.

Question-Why is the normal line important in the study of reflection?
Answer- The normal line, drawn perpendicular to the reflecting surface at the point of incidence, serves as a reference for measuring the angles of incidence and reflection. It is crucial for determining how light is reflected off a surface.

Question-What is the relationship between the angle of incidence and the angle of reflection according to the law of reflection?
Answer- According to the law of reflection, the angle of incidence (∠i) is always equal to the angle of reflection (∠r), regardless of the angle at which light hits the surface.

Question-How does the image formed by a plane mirror differ from that formed by other reflective surfaces?
Answer- The image formed by a plane mirror is always a virtual image, meaning it cannot be projected onto a screen. It appears erect and is of the same size as the object, located at the same distance behind the mirror as the object is in front of it.

Question-What is lateral inversion and why is it important in practical applications like on an ‘AMBULANCE’ sign?
Answer- Lateral inversion is the phenomenon where the right side of an object appears as the left side in the image, and vice versa. This is crucial for applications like the ‘AMBULANCE’ sign, where the text is written in reverse so that when viewed in a rearview mirror, it appears correctly, helping drivers ahead of the ambulance to read it properly and give way.

Question-What happens to the characteristics of the image formed by a concave mirror when the object is very close to it?
Answer- When an object is placed very close to a concave mirror, the image formed is erect and virtual, as opposed to the typical real and inverted image formed at other distances.

Question-How do convex mirrors differ from concave mirrors in terms of the images they form?
Answer- Convex mirrors always form images that are virtual, erect, and diminished, regardless of the object’s distance from the mirror, unlike concave mirrors that can form real, inverted, and magnified images under certain conditions.

Question-What did Sir Isaac Newton discover about white light and how did he demonstrate it?
Answer– Newton discovered that white light is composed of seven different colours. He demonstrated this by passing a beam of white light through a glass prism, resulting in the formation of a spectrum displaying these colours.

Question-What are the main differences between diffused (irregular) reflection and regular reflection in terms of image formation and surface texture?
Answer- Regular reflection occurs on smooth, shiny surfaces and produces clear, well-defined images due to uniform reflection of light rays. In contrast, diffused reflection happens on rough, irregular surfaces, resulting in scattered light rays that do not form clear images.

Question-Explain the principle behind the formation of rainbows.
Answer- Rainbows are formed when sunlight is dispersed by raindrops in the atmosphere. This natural phenomenon involves both refraction (bending of light) and reflection within the raindrops, leading to the colourful arc with red on the outer part and violet on the inner part.

Question-How do concave mirrors enhance safety in automotive lighting?
Answer- Concave mirrors are used in headlights of vehicles to focus and direct light into a strong, straight beam, thereby enhancing visibility and safety.

Question-Why are convex mirrors preferred in vehicle rearview mirrors and security applications?
Answer- Convex mirrors are used in rearview mirrors and for security because they provide a wider field of view, crucial for driving safety and monitoring larger areas in security settings.

Question-What is the unique characteristic of the image formed by a plane mirror in terms of size and position?
Answer- In a plane mirror, the image is always of the same size as the object and appears to be at the same distance behind the mirror as the object is in front of it.

Question-How does the design of convex lenses make them suitable for magnifying glasses and optical instruments?
Answer– Convex lenses, being thicker in the centre and narrower at the edges, can focus light and create clear images, making them ideal for magnifying glasses and optical instruments like cameras and telescopes.Question-What practical purpose does the lateral inversion phenomenon serve in emergency services?
Answer- Lateral inversion, where the right side of an object appears as the left in its image in plane mirrors, is used to write “AMBULANCE” in reverse. This ensures that when viewed in a rearview mirror, the text appears correctly, helping drivers recognize the emergency vehicle and respond quickly.