Class 2nd — Science

Chapter 1: Light, Shadow & Reflection

प्रकाश, परछाई और परावर्तन

📚 Chapter Theory & Introduction

Can you see anything in a completely dark room? No! We need Light to see the things around us. The Sun is the main source of light on Earth during the day. At night, we use bulbs, candles, and torches.

क्या आप एक बिल्कुल अंधेरे कमरे में चीजें देख सकते हैं? नहीं! हमें अपने आसपास की चीजों को देखने के लिए प्रकाश (Light) की जरूरत होती है। सूर्य पृथ्वी पर प्रकाश का मुख्य स्रोत है।

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Sources of Light & Shadows (प्रकाश के स्रोत और परछाई)

1. Sources of Light (प्रकाश के स्रोत)

  • Luminous Objects (दीप्त वस्तुएं): Objects that give out their own light. Examples: Sun, Stars, Electric Bulb, Burning Candle.
  • Non-Luminous Objects (अदीप्त वस्तुएं): Objects that do not give out their own light. Examples: Moon, Chair, Book, Table, Tree.

जो चीजें खुद का प्रकाश देती हैं उन्हें दीप्त (Luminous) कहते हैं, और जो खुद का प्रकाश नहीं देतीं उन्हें अदीप्त (Non-Luminous) कहते हैं।

2. What is a Shadow? (परछाई क्या है?)

When an object blocks the path of light, a dark patch is formed on the opposite side. This dark patch is called a Shadow.

जब कोई वस्तु प्रकाश के रास्ते को रोकती है, तो दूसरी तरफ एक अंधेरा या काला हिस्सा बनता है। इसे ही हम परछाई कहते हैं।

💡 Properties of Shadows (परछाई की विशेषताएं)

* A shadow is always formed on the **opposite side** of the light source.
* A shadow is always **dark or black**, no matter what color the object is.
* The size of a shadow changes with the position of the Sun. Shadows are **long in the morning and evening**, and **shortest at noon** (when the sun is directly overhead).

3. What is Reflection? (परावर्तन क्या है?)

When light falls on a smooth and shiny surface (like a mirror), it bounces back. This bouncing back of light is called Reflection. Reflection helps us to see our face in the mirror.

जब प्रकाश किसी चमकदार सतह (जैसे शीशे) पर गिरता है, तो वह टकराकर वापस लौटता है। प्रकाश के इस टकराकर लौटने को परावर्तन (Reflection) कहते हैं।

📝 Class Exercise (20 IMP Questions)

Click on the "Check Answer" button to see the correct answer.

Q1. What do we need to see things around us?

Answer: We need Light (प्रकाश) to see things.

Q2. What is the main natural source of light on Earth?

Answer: The Sun.

Q3. What are luminous objects?

Answer: Objects that give out their own light are called luminous objects.

Q4. Give two examples of man-made luminous objects.

Answer: Electric bulb and Torch.

Q5. Does the Moon have its own light?

Answer: No, the Moon shines because it reflects the light of the Sun. It is a non-luminous object.

Q6. Is a wooden table a luminous or non-luminous object?

Answer: Non-luminous object.

Q7. When is a shadow formed?

Answer: A shadow is formed when an object blocks the path of light.

Q8. What is the color of a shadow of a bright red ball?

Answer: Black. Shadows are always dark or black, regardless of the object's color.

Q9. On which side of the light source is a shadow formed?

Answer: On the opposite side of the light source.

Q10. At what time of the day are shadows the shortest?

Answer: At noon (12 o'clock), when the sun is directly above our head.

Q11. At what times of the day are shadows very long?

Answer: In the morning and in the evening.

Q12. What is the bouncing back of light from a shiny surface called?

Answer: Reflection (परावर्तन).

Q13. Which object is best suited to see our own reflection?

Answer: A Mirror (शीशा).

Q14. True or False: We can see a shadow in a pitch-black room with no light.

Answer: False. We need a source of light to form a shadow.

Q15. Are stars luminous or non-luminous?

Answer: Stars are luminous objects because they have their own light.

Q16. Can light pass through a brick wall?

Answer: No, a brick wall blocks light completely and forms a dark shadow.

Q17. True or False: Light travels in a straight line.

Answer: True. Light always travels in a straight line.

Q18. Does a clear glass window form a dark shadow?

Answer: No, because clear glass lets light pass through it easily.

Q19. Why can we see our image on a clean water surface?

Answer: Due to the reflection of light from the smooth water surface.

Q20. What happens to the size of your shadow as you move closer to a street light?

Answer: The size of your shadow changes and becomes smaller or larger based on the angle.

🧠 Interactive Lesson Quiz

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