Light: Mirrors and Lenses Class 8 Science Curiosity Chapter 10 Solutions
🟢 1. A light ray is incident on a mirror and gets reflected by it (Fig. 10.21). The angle made by the incident ray with the normal to the mirror is 40°. What is the angle made by the reflected ray with the mirror?
(i) 40° (ii) 50° (iii) 45° (iv) 60°
🧠 Explanation:
📌 Given:
- Angle of incidence (i) = 40°
👉 By law of reflection (परावर्तन का नियम):
- Angle of reflection (r) = 40°
📐 Angle with mirror:
👉 = 90° – 40° = 50°
🟢 2. Fig. 10.22 shows three different situations where a light ray falls on a mirror:
Draw the reflected ray in each case (Use a ruler and protractor for accurate drawing). What is the angle of reflection in each case?
Answer:
Class 8 Science Curiosity Chapter 10 Question 3 and 4
🟢 Class 8 Science Curiosity Chapter 10 Question 3 and 4
🟢 3. In Fig. 10.23, the cap of a sketch pen is placed in front of three types of mirrors.
✅ Answer (Concept Based):
🪞 Three types of mirrors:
🔹 Plane Mirror (समतल दर्पण)
- Image same size 📏
- Erect (सीधी)
- Laterally inverted 🔄
🔹 Concave Mirror (अवतल दर्पण)
- Close object → Image बड़ा 🔍
- Far object → Image छोटा / inverted
🔹 Convex Mirror (उत्तल दर्पण)
- Always small image 🔽
- Always erect ✔️
- Wider view (rear-view mirror 🚗)
Answer:
4. In Fig. 10.24 the cap of a sketch pen is placed behind a convex lens, a concave lens and a flat transparent glass piece — all at the same distance.
Match each image with the correct type of lens or glass.
Image | Lens/glass type |
(i) Flat transparent glass piece | |
(ii) Convex lens | |
(iii) Concave lens |
Answer:
🟢 Question 5 and 6 of Class 8 Science Curiosity Chapter 10
🟢 5. When the light is incident along the normal on the mirror, which of the following statements is true:
✅ Answer:
👉 Correct option: (ii) Angle of incidence is 0°
🧠 Explanation:
📌 Normal (लंब) = imaginary line perpendicular to mirror
👉 When light falls along normal:
- Angle of incidence (i) = 0°
- Angle of reflection (r) = 0°
🔄 Ray same path me wapas reflect hoti hai
🟢 6. Three mirrors — plane, concave and convex are placed in Fig. 10.25. On the basis of the images of the graph sheet formed in the mirrors, identify the mirrors and write their names above the mirrors.
✅ Answer:
🪞 Identification based on image:
🔹 Plane Mirror (समतल दर्पण)
- Image same size 📏
- Straight lines remain straight ✔️👉 Graph sheet looks normal
🔹 Concave Mirror (अवतल दर्पण)
- Image may be enlarged / inverted 🔍
- Lines may appear curved/distorted👉 Graph appears bigger or upside-down
🔹 Convex Mirror (उत्तल दर्पण)
- Image always smaller (छोटी) 🔽
- Wider field of view 👀👉 Graph looks shrunk
📌 Conclusion Trick (Exam Tip):
- Same size → Plane
- Bigger/Distorted → Concave
- Smaller → Convex
Class 8 Science Curiosity Chapter 10 Question 7, 8 and 9
🟢 7. In a museum, a woman walks towards a large convex mirror (Fig. 10.26). She will see that:
✅ Answer:
👉 Correct option: (iv) her erect image keeps increasing in size
🧠 Explanation:
🪞 Convex Mirror (उत्तल दर्पण):
- Image always erect (सीधी) ✔️
- Image always diminished (छोटी)
👉 But as object comes closer:
- Image size increase hota hai 📈
- Still remains smaller than object
See Answer (iii) her inverted image keeps increasing in size and eventually it becomes erect and magnified.
🟢 8. Hold a magnifying glass over text and identify the distance where you can see the text bigger than they are written. Now move it away from the text. What do you notice? Which type of lens is a magnifying glass?
✅ Answer:
🔍 Observation:
👉 Close distance:
- Text appears bigger (विस्तारित) 🔎
👉 Move away:
- Image may become blurred / inverted / smaller
🧠 Concept:
🔎 Magnifying glass = Convex Lens (उत्तल लेंस)
- Near object → enlarged & erect image
- Far object → inverted image
🟢 9. Match the entries in Column I with those in Column II.
Column I | Column II |
(i) Concave mirror | (a) Spherical mirror with a reflecting surface that curves inwards. |
(ii) Convex mirror | (b) It forms an image which is always erect and diminished in size. |
(iii) Convex lens | (c) Object placed behind it may appear inverted at some distance. |
(iv) Concave lens | (d) Object placed behind it always appears diminished in size. |
✅ Answer:
Column I | Column II |
(i) Concave mirror | (a) ✔️ |
(ii) Convex mirror | (b) ✔️ |
(iii) Convex lens | (c) ✔️ |
(iv) Concave lens | (d) ✔️ |
📌 Quick Trick 🧠:
- Convex mirror → always small
- Concave mirror → inward curve
- Convex lens → can invert
- Concave lens → always small
🟢 Class 8 Science Curiosity Chapter 10 Question 10, 11 and 12
🟢 10. Assertion: Convex mirrors are preferred for observing the traffic behind us.
Reason: Convex mirrors provide a significantly larger view area than plane mirrors.
✅ Answer:
👉 Correct option: (i) ✔️
🧠 Explanation:
🚗 Convex mirror:
- Wider field of view 👀
- Covers large area
👉 That’s why used as rear-view mirrors
📌 Reason correctly explains Assertion ✔️
🟢 11. In Fig. 10.27, note that O stands for object, M for mirror, and I for image. Which of the following statements is true?
✅ Answer:
👉 Correct option: (iii) Figure (a) indicates a concave mirror and Figure (b) indicates a convex mirror
🧠 Explanation:
🪞 Concave mirror:
- Can form real/inverted image
🪞 Convex mirror:
- Always forms virtual, erect, smaller image
👉 Diagram observation se identify hota hai ✔️
See Answer(iv) Figure (a) indicates a plane mirror and Figure (b) indicates a convex mirror.
12. Place a pencil behind a transparent glass tumbler (Fig. 10.28a). Now fill the tumbler halfway with water (Fig. 10.28b). How does the pencil appear when viewed through the water? Explain why its shape appears changed.
