a. Convex mirror
b. Concave mirror
c. virtual and Inverse
d. Convex lens
e. Concave lens
f. diffuse light
g. Seven colours
h. virtual
i. Convex lens
j. Concave lens
k. Real image
l. converges light
m. plane mirror
n. Dispersion
o. Convex mirror
1. What do we call the phenomenon in which light returns after striking a surface?
Answer: Reflection.
2. What is the name of the ray that travels towards a reflecting surface?
Answer: Incident ray.
3. What do we call the ray that leaves the surface after reflection?
Answer: Reflected ray.
4. What is the imaginary line drawn at $90^\circ$ to a reflecting surface at the point where light strikes it?
Answer: The normal.
5. What is the angle formed between the incident ray and the normal called?
Answer: Angle of incidence.
6. What is the angle between the reflected ray and the normal known as?
Answer: Angle of reflection.
7. According to the law of reflection, how are the angle of incidence and the angle of reflection related?
Answer: They are equal.
$$
\angle i = \angle r
$$
8. At what point do the incident ray, reflected ray and normal meet?
Answer: At the point of incidence.
9. Which phenomenon explains the apparent interchange of the left and right sides in a plane mirror?
Answer: Lateral inversion.
10. Can the image formed by a plane mirror be obtained on a screen?
Answer: No, because it is a virtual image.
11. State the two important laws of reflection.
Answer:
* The angle of incidence is equal to the angle of reflection.
* The incident ray, reflected ray and the normal at the point of incidence lie in the same plane.
12. Describe the nature of the image formed by a plane mirror.
Answer: A plane mirror forms an image that is virtual, erect and equal in size to the object.
13. Why can a virtual image not be obtained on a screen?
Answer: A virtual image is formed by the apparent intersection of light rays and not by the actual convergence of rays. Therefore, it cannot be captured on a screen.
14. A concave mirror is used to observe an object placed very close to it. What type of image may be formed?
Answer: The image can be virtual, erect and enlarged.
15. Can a concave mirror produce both real and virtual images? Explain briefly.
Answer: Yes. Depending on the position of the object, a concave mirror can form either a real, inverted image or a virtual, erect image.
16. What are the characteristics of the image always formed by a convex mirror?
Answer: The image is always erect and diminished.
17. What kind of image does a concave lens always produce?
Answer: It always produces an erect and diminished image.
18. How can you identify a convex lens by observing its shape?
Answer: A convex lens is thicker at the centre and thinner near its edges.
19. How can you identify a concave lens by observing its thickness?
Answer: A concave lens is thinner at the centre and thicker near its edges.
20. Why is a concave lens known as a diverging lens?
Answer: It causes parallel rays of light passing through it to spread out or diverge.
21. Why is a convex lens called a converging lens?
Answer: It brings parallel rays of light closer together and makes them meet at a point.
22. What happens when sunlight passes through a convex lens and falls on a sheet of paper?
Answer: The lens converges the sunlight to a small region, producing a bright spot.
23. A student draws a line perpendicular to a mirror at the point where a ray strikes it. What does this line represent?
Answer: It represents the normal.
24. If the angle of incidence is $35^\circ$, what will be the angle of reflection?
Answer: According to the first law of reflection,
$$
\angle i = \angle r
$$
Therefore,
$$
\angle r = 35^\circ
$$
25. A ray of light strikes a mirror. Which three elements must lie in the same plane according to the laws of reflection?
Answer: The incident ray, the reflected ray and the normal.
26. Why is a convex mirror useful when a wide field of view is required?
Answer: A convex mirror forms diminished, erect images and allows a larger area to be viewed.
27. An object is moved farther away from a convex mirror. What happens to its image?
Answer: The image remains erect and becomes more diminished.
28. An object is placed very close to a convex lens. What kind of image is observed?
Answer: The image appears erect and magnified.
29. How does the image change when an object is moved farther away from a convex lens, according to the concept discussed in the transcript?
Answer: The image becomes inverted and smaller.
30. A lens is thickest at its centre. Predict whether it converges or diverges light.
Answer: It is a convex lens and converges light.
31. A lens is thinner at its centre but thicker near the edges. Identify the lens and state its effect on light rays.
Answer: It is a concave lens, and it causes light rays to diverge.
32. Which type of lens is present in the human eye?
Answer: A convex lens.
33. How does the lens of the human eye help us see both nearby and distant objects?
Answer: The eye lens can change its shape slightly to adjust its focusing ability for objects at different distances.
34. Riya stands in front of a plane mirror and notices that her right hand appears to be on the opposite side in the image. Which property of the mirror image is responsible for this?
Answer: Lateral inversion.
35. A dentist needs a mirror that can sometimes produce a magnified upright image of a nearby object. Which mirror would be suitable?
Answer: A concave mirror.
36. A shopkeeper wants to observe a large area behind the counter using a single mirror. Which mirror would be more suitable?
Answer: A convex mirror because it provides a wider field of view.
37. A student allows sunlight to pass through a lens and obtains a concentrated bright spot on a paper. What type of lens is being used?
Answer: A convex lens.
38. A lens causes a parallel beam of light to spread outward after passing through it. Identify the lens.
Answer: A concave lens.
39. An image is erect, virtual and smaller than the object. Name two optical devices discussed in the transcript that can produce such an image.
Answer:
* Convex mirror
* Concave lens
40. An object is placed close to an optical device and its image appears upright and enlarged. Which two devices discussed in the lesson can show this behaviour?
Answer:
* Concave mirror
* Convex lens