Maharashtra Board Class 9 Science Reflection of Light Textbook Question Answers and Important Notes from the Chapter.
Explain the difference between a plane mirror, a concave mirror and a convex mirror with respect to the type and size of the images produced.
| Mirror Type | Reflection Surface | Image Type | Image Size |
| Plane Mirror | Flat and smooth surface | Virtual | Same size as the object |
| Concave Mirror | Inner curved surface | Real | Enlarged or reduced based on object distance |
| Convex Mirror | Outer curved surface | Virtual | Always smaller than the object regardless of distance |
Describe the positions of the source of light with respect to a concave mirror in 1. Torch light 2. Projector lamp 3. Floodlight.
| Light Source | Position with Respect to Concave Mirror |
| Torch Light | Positioned at the Focus or between Focus and Pole for an erect, virtual, and magnified image |
| Projector Lamp | Typically positioned at or near the Focus for a parallel beam or a slightly beyond the Center of Curvature for a bright beam |
| Floodlight | Placed a little beyond the Center of Curvature to produce a bright and widespread beam |
Why are concave mirrors used in solar devices?
Concave mirrors are used in solar devices because:
- They focus sunlight to a specific point, increasing energy intensity.
- They efficiently collect and concentrate sunlight for various applications.
- They can be used in different solar devices like cookers, heaters, and power generators.
Why are the mirrors fitted on the outside of cars convex?
Mirrors fitted on the outside of cars are convex because:
- Convex mirrors provide a broader field of view, helping drivers see more of the surroundings.
- Convex mirrors make parking easier as they display a wider perspective
- Convex mirrors produce smaller images, allowing more to be seen within a limited space.
- They reduce glare from headlights of vehicles behind, improving nighttime visibility.
Why does obtaining the image of the sun on a paper with the help of a concave mirror burn the paper?
Obtaining the image of the sun on a paper with a concave mirror can burn the paper because:
- The concave mirror focuses sunlight onto a small area on the paper.
- The concentrated sunlight raises the temperature of the paper significantly.
- The high temperature surpasses the paper’s ignition point, causing it to catch fire.
Which type of mirrors are used in the following?
Periscope, floodlights, shaving mirror, kaleidoscope, street lights, headlamps of a car. tabular form
| Device | Type of Mirror Used |
| Periscope | Plane mirror |
| Floodlights | Concave mirror |
| Shaving mirror | Concave mirror |
| Kaleidoscope | Multiple plane mirrors |
| Street lights | Convex mirror |
| Headlamps of a car | Convex mirror |
Important Points
Introduction:
- Light is essential for perceiving our surroundings and enjoying natural wonders.
- Light is electromagnetic radiation, enabling vision.
Plane Mirrors:
- Reflective surfaces that create clear images are mirrors.
- Two types: plane mirrors and spherical mirrors.
- Plane mirrors reflect with regular reflection, producing clear images.
- Images in plane mirrors are laterally inverted but of the same size as the source.
Spherical Mirrors:
- Curved mirrors, concave (inner surface reflects) and convex (outer surface reflects).
- Concave mirrors are focusing mirrors, producing real images.
- Convex mirrors are dispersing mirrors, producing virtual and smaller images.
Determining Mirror Type:
- Concave mirrors magnify when close and diminish when distant.
- Convex mirrors produce erect and smaller images, regardless of distance.
Applications of Mirrors:
- Concave mirrors: Barber shops, dental hospitals, torches, floodlights, solar energy equipment.
- Convex mirrors: Car side mirrors, large mirrors at gates and squares.
Key Points-
The image in front of the mirror which can be obtained on a screen is called a real image.
The image which is behind the mirror and thus cannot be obtained on a screen is called a virtual image.
Radius of curvature : The radius of the sphere of which the mirror is a part, is called the radius of curvature of the mirror.
Focal length : The distance (f) between the pole and the principal focus of the mirror is called the focal length. This distance is half of the radius of curvature of the mirror.
