Light: Mirrors and Lenses
Short Questions
1. What is a spherical mirror?
Answer:- A mirror with a curved surface, like part of a sphere.
2.Name the two types of spherical mirrors.
Answer:- Concave and convex mirrors.
3.What is a concave mirror?
Answer:- A mirror that curves inward.
4.What is a convex mirror?
Answer:- A mirror that curves outward.
5.How does a plane mirror form an image?
Answer:- It forms an erect image of the same size as the object.
6.What kind of image does a convex mirror always form?
Answer:- An erect and diminished image.
7.What happens to the image in a concave mirror when the object moves farther away?
Answer:- The image becomes inverted and smaller.
8.What is the first law of reflection?
Answer:- The angle of incidence equals the angle of reflection.
9.What is the second law of reflection?
Answer:- The incident ray, normal, and reflected ray lie in the same plane.
10.What does a convex lens do to light beams?
Answer:- It converges light beams.
11.What does a concave lens do to light beams?
Answer:- It diverges light beams.
12.What type of lens is a magnifying glass?
Answer:- A convex lens.
13.Where are convex mirrors used in vehicles?
Answer:- As side-view mirrors.
14.What is the shape of a water drop acting as a lens?
Answer:- It has a curved surface.
15.Why do convex mirrors show objects closer than they appear?
Answer:- They form smaller images, making objects seem farther away.
Long Questions
1. How can you distinguish between a concave and convex mirror by looking at their side view?
Answer:- A concave mirror curves inward, like a cave, while a convex mirror bulges outward. You can identify them by checking the direction of the curve from the side.
2. Why do convex mirrors provide a wider view compared to plane mirrors?
Answer:- Convex mirrors curve outward, reflecting light from a larger area. This makes them ideal for seeing more of the surroundings, like in vehicle side mirrors.
3. Explain how a concave mirror is used in a torch or car headlight.
Answer:- A concave mirror reflects light from a bulb placed at its focus, converging it into a strong beam. This helps direct light forward for better illumination.
4. What happens to the image in a convex lens when the object is moved farther away?
Answer:- When the object is close, the image is erect and enlarged. As it moves farther, the image becomes inverted and may get smaller.
5. How does a water drop act as a lens, and what kind of lens is it?
Answer:- A water drop’s curved surface bends light, making objects appear larger. It acts like a convex lens due to its outward curve.
6. Why are convex mirrors used at road intersections?
Answer:- Convex mirrors provide a wide field of view, showing traffic from multiple directions. This helps drivers see around corners and avoid collisions.
7. What are the differences between images formed by concave and convex lenses?
Answer:- A concave lens always forms erect, diminished images. A convex lens can form erect or inverted images, which may be enlarged or diminished, depending on the object’s distance.
8. How can you demonstrate that light travels in a straight line using a mirror?
Answer:- Shine a beam of light through a slit onto a mirror and observe the reflected beam. The straight path of the incident and reflected beams shows light travels in a straight line.
9. Why is a concave mirror used by dentists?
Answer:- A concave mirror provides an enlarged, erect image when held close to teeth. This helps dentists see small details clearly for examination.
10. What did you learn from Activity 10.6 about the reflection of parallel beams by different mirrors?
Answer:- Plane mirrors reflect parallel beams as parallel. Concave mirrors converge them, while convex mirrors diverge them, due to their curved surfaces.
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