Chapter 14: Light and the Formation of Shadows
Solved textbook questions with step-by-step explanations.
Grade 6 Q&A: Chapter 14: Light and the Formation of Shadows
Welcome to the Questions and Answers section for Grade 6 Environmental Studies (Part One), Chapter 14: "Light and the Formation of Shadows." This chapter delves into the fascinating world of light, its sources, how it travels, and how it interacts with different types of objects to form shadows. We will learn about luminous and non-luminous objects, transparent, translucent, and opaque materials, and the conditions necessary for a shadow to be formed.
Important Questions and Answers
Q1: What is light?
Answer: Light is a form of energy that enables us to see objects. It travels in straight lines.
Q2: What are luminous objects? Give examples.
Answer: Luminous objects are those that produce their own light. Examples include the Sun, a star, a burning candle, a light bulb, and a firefly.
Q3: What are non-luminous objects? Give examples.
Answer: Non-luminous objects are those that do not produce their own light but are seen when light from a luminous source falls on them and is reflected. Examples include the Moon, a table, a book, and a tree.
Q4: How does light travel?
Answer: Light travels in straight lines. This property of light is called rectilinear propagation of light.
Q5: What is a ray of light?
Answer: A ray of light is a single, narrow path along which light travels. It is usually represented by a straight line with an arrow indicating the direction of light.
Q6: What is a beam of light?
Answer: A beam of light is a collection of several rays of light traveling together.
Q7: What are transparent objects? Give examples.
Answer: Transparent objects are those through which light can pass completely, allowing us to see clearly through them. Examples include clear glass, air, and pure water.
Q8: What are translucent objects? Give examples.
Answer: Translucent objects are those through which light can pass partially, but we cannot see clearly through them. The light gets scattered. Examples include frosted glass, butter paper, and thin plastic sheets.
Q9: What are opaque objects? Give examples.
Answer: Opaque objects are those through which light cannot pass at all. They block light completely. Examples include a wooden door, a brick wall, and a metal sheet.
Q10: What is a shadow?
Answer: A shadow is a dark area formed when an opaque object blocks the path of light from a source.
Q11: What are the necessary conditions for the formation of a shadow?
Answer: The three necessary conditions for the formation of a shadow are:
- A source of light.
- An opaque object to block the light.
- A screen or surface for the shadow to be formed on.
Q12: Does the size of a shadow change? If so, how?
Answer: Yes, the size of a shadow can change. It depends on the distance between the light source and the object, and the distance between the object and the screen. If the light source is closer to the object, the shadow will be larger. If the object is closer to the screen, the shadow will be smaller.
Q13: Does the shape of a shadow change? If so, how?
Answer: Yes, the shape of a shadow can change depending on the angle at which light falls on the object and the orientation of the object relative to the light source and screen.
Q14: What is the difference between umbra and penumbra?
Answer:
- Umbra: The darkest, central part of a shadow where no light from the source reaches.
- Penumbra: The lighter, outer part of a shadow where some light from the source is blocked, but not all. It is a partial shadow.
Q15: Why do we see shadows only when there is a light source?
Answer: Shadows are formed by the absence of light. Without a light source, there is no light to be blocked by an opaque object, and thus no shadow can be formed.
Q16: Can a transparent object form a shadow? Why or why not?
Answer: No, a transparent object cannot form a distinct shadow because it allows almost all light to pass through it, so it does not block the light to create a dark area.
Q17: Can a translucent object form a shadow?
Answer: A translucent object can form a very faint or blurry shadow because it scatters some light and blocks a small portion, but not completely.
Q18: Explain why a shadow is always black, regardless of the color of the object.
Answer: A shadow is always black because it is an area where light is blocked. It is the absence of light, not the color of the object, that determines the color of the shadow.
Q19: What is a pinhole camera? How does it work?
Answer: A pinhole camera is a simple camera without a lens, using a small hole (pinhole) to focus light. It works on the principle that light travels in straight lines. Light from an object passes through the pinhole and forms an inverted image on the opposite screen inside the camera.
Q20: Why is the image formed by a pinhole camera inverted?
Answer: The image formed by a pinhole camera is inverted because light rays from the top of the object pass through the pinhole and reach the bottom of the screen, and light rays from the bottom of the object reach the top of the screen, due to the rectilinear propagation of light.
Q21: Give an example of a natural source of light.
Answer: The Sun is the most prominent natural source of light.
Q22: Give an example of an artificial source of light.
Answer: An electric bulb or a torch are examples of artificial sources of light.
Q23: How does the Earth form a shadow during a solar eclipse?
Answer: During a solar eclipse, the Moon comes between the Sun and the Earth. The Moon, being an opaque object, blocks the Sun's light, and its shadow falls on certain parts of the Earth.
Q24: How does the Earth form a shadow during a lunar eclipse?
Answer: During a lunar eclipse, the Earth comes between the Sun and the Moon. The Earth, being an opaque object, blocks the Sun's light from reaching the Moon, and the Earth's shadow falls on the Moon.
Q25: Why do shadows appear longer in the morning and evening, and shorter at noon?
Answer: Shadows appear longer in the morning and evening because the Sun is low in the sky, and its rays hit objects at a shallow angle, casting long shadows. At noon, the Sun is directly overhead, and its rays hit objects more vertically, resulting in shorter shadows.
Q26: What is the significance of light in our daily lives?
Answer: Light is essential for us to see the world around us. It also plays a crucial role in photosynthesis for plants, provides warmth, and is used in various technologies like cameras, lasers, and optical fibers.
Q27: Can light bend around corners? Explain.
Answer: No, light generally travels in straight lines and does not bend around corners. This is why opaque objects cast sharp shadows. If light could bend, shadows would not be clearly defined.
Exercise Solutions
Q1: Fill in the blanks.
- Light travels in a straight line.
- Objects that produce their own light are called luminous objects.
- A shadow is formed when an opaque object blocks light.
- The darkest part of a shadow is called the umbra.
- A pinhole camera forms an inverted image.
Q2: True or False.
- The Moon is a luminous object. False
- A clear glass allows light to pass through completely. True
- Shadows are always black. True
- The size of a shadow never changes. False
- A solar eclipse occurs when the Earth's shadow falls on the Moon. False (That's a lunar eclipse)
Q3: Answer the following questions.
- What is the difference between luminous and non-luminous objects?
Answer: Luminous objects produce their own light (e.g., Sun, bulb), while non-luminous objects do not produce light but reflect light from other sources (e.g., Moon, book). - Explain how a shadow is formed.
Answer: A shadow is formed when an opaque object comes in the path of light from a source. Since light travels in straight lines, the opaque object blocks the light, creating a dark area behind it on a screen or surface, which is the shadow. - Name three types of objects based on how light passes through them. Give an example of each.
Answer:- Transparent: Light passes completely (e.g., clear glass).
- Translucent: Light passes partially, scattered (e.g., frosted glass).
- Opaque: Light does not pass at all (e.g., wooden door).
- What are the essential things required to form a shadow?
Answer: The essential things required to form a shadow are a source of light, an opaque object, and a screen or surface. - Why do shadows appear longer in the morning and evening?
Answer: Shadows appear longer in the morning and evening because the Sun is low in the sky, and its rays hit objects at an oblique (slanted) angle, extending the shadow's length.
Q4: Give reasons.
- We cannot see through a wooden door.
Reason: We cannot see through a wooden door because wood is an opaque material. Opaque objects completely block the passage of light, preventing light from passing through them to our eyes. - A shadow is formed behind a person standing in sunlight.
Reason: A shadow is formed behind a person standing in sunlight because the person's body is an opaque object. When this opaque object blocks the path of the Sun's light, an area where light cannot reach is created behind them, forming a shadow on the ground or surface. - The image formed by a pinhole camera is inverted.
Reason: The image formed by a pinhole camera is inverted because light travels in straight lines. Light rays from the top of the object travel downwards through the pinhole to reach the bottom of the screen, and light rays from the bottom of the object travel upwards through the pinhole to reach the top of the screen, resulting in an inverted image.
References
- Maharashtra State Board Environmental Studies (Part One) Standard Six Textbook (2015 Edition) - Chapter 14: Light and the Formation of Shadows.
- Maharashtra State Board 6th Standard Environmental Studies Syllabus.
- Balbharati Environmental Studies Part 1 Textbook.