Science [4 Mark Questions]

1. At F
2. Diminished
3. At C
4. Magnified
5. Virtual and erect

Construction:

1. Take three equal sized plane mirror strips and arrange them in such a way that they form an equilateral triangle.
2. Cover the sides of the mirrors with a chart paper. With the help of a chart paper cover the bottom of the mirrors also.
3. Put some coloured things such as pieces of bangles and beads inside it.
4. Now, cover the top portion with the chart paper and make a hole in it to see.
5. You can wrap the entire piece with coloured papers to make it attractive.
6. Now, rotate it and see through its opening. You can see the beautiful patterns.

Regular reflection:

1. When a beam of light (collection of parallel rays) falls on a smooth surface, it gets reflected. After reflection, the reflected rays will be parallel to each other.
2. Here, the angle of incidence and the angle of reflection of each ray will be equal.
3. Hence, the law of reflection is obeyed in this case and thus a clear image is formed.
4. This reflection is called ‘regular reflection’ or ‘specular reflection’.

Example : Reflection of light by a plane mirror and reflection of light from the surface of still water.

Irregular reflection:

1. In the case of a body having a rough or irregular surface, each region of the surface is inclined at different angles.
2. When light falls on such a surface, the light rays are reflected at different angles. In this case, the angle of incidence and the angle of reflection of each ray are not equal.
3. Hence, the law of reflection is not obeyed in this case and thus the image is not clear. Such a reflection is called ‘irregular reflection’ or ‘diffused reflection’.

Example : Reflection of light from a wall.

A ray of light, falling on a body having a shiny polished and smooth surface alone is bounced back. This bouncing back of the light rays as they fall on the smooth, shiny, and polished surface is called reflection.

• Regular reflection:

1. When a beam of light (collection of parallel rays) falls on a smooth surface, it gets reflected.
2. After reflection, the reflected rays will be parallel to each other. Here, the angle of incidence and the angle of reflection of each ray will be equal.
3. Hence, the law of reflection is obeyed in this case and thus a clear image is formed. This reflection is called ‘regular reflection’ or ‘specular reflection’.

• Irregular reflection:

1. In the case of a body having a rough or irregular surface, each region of the surface is inclined at different angles.
2. When light falls on such a surface, the light rays are reflected at different angles.
3. In this case, the angle of incidence and the angle of reflection of each ray are not equal.
4. Hence, the law of reflection is not obeyed in this case and thus the image is not clear. Such a reflection is called ‘irregular reflection’ or ‘diffused reflection’.

• Concave mirrors:

1. Concave mirrors are used while applying make–up or shaving, as they provide a magnified image.
2. They are used in torches, search lights, and head lights as they direct the light to a long distance.

• Convex mirrors:

1. Convex mirrors are used in vehicles as rearview mirrors because they give an upright image and provide a wider field of view as they are curved outwards.
2. They are found in the hallways of various buildings including hospitals, hotels, schools, and stores. They are usually mounted on a wall or ceiling where hallways make sharp turns.