Notes On Reflection of Light - CBSE Class 7 Science

Reflection of Light

The path of light is always straight and never curved. Examples to show that light travels in a straight line are light emitted by a torch light and light emitted from the headlights of a vehicle. The direction of light can be changed only by reflection. The bouncing of light by any surface is called reflection of light.

Image Formed by a Plane Mirror

Due to the reflection of light, the impression of an object formed in a mirror is called the image of the object. As the distance of the object from the mirror increases, the distance of the image from the mirror also increases. The concept that images in a plane mirror are located at the same distance behind the mirror as the object in front of it is mainly used in interior decoration and in architecture to make rooms appear brighter and bigger. Moreover, placing a mirror near lights, chandeliers and table lamps reflects the light over a larger area, and makes the room appear brighter. Images that cannot be captured on a screen are called virtual images.

Left–Right Inversion

As the name suggests, images are laterally inverted, i.e. the right part of an object appears on the left in its image, and the left part of the object appears on the right. For example, the word AMBULANCE is painted left-right inverted on the ambulance so that when the driver of a vehicle in front looks into his rear-view mirror, he can make out the word AMBULANCE quickly and give way.

Characteristics of Image Formed in a Plane Mirror

The image formed by a plane mirror is:
     •  of the same size as that of the object
     •  left-right inverted
     •  erect and virtual
     •  as far behind the mirror as the object is in front of it.

A mirror maze is created based on the principle of reflection in plane mirrors. The maze has several plane mirrors placed at fixed angles to each other. When a person enters a mirror maze, he finds several images of himself and several passages. There is only one passage that is real, while all the others are just images.

Summary

Reflection of Light

The path of light is always straight and never curved. Examples to show that light travels in a straight line are light emitted by a torch light and light emitted from the headlights of a vehicle. The direction of light can be changed only by reflection. The bouncing of light by any surface is called reflection of light.

Image Formed by a Plane Mirror

Due to the reflection of light, the impression of an object formed in a mirror is called the image of the object. As the distance of the object from the mirror increases, the distance of the image from the mirror also increases. The concept that images in a plane mirror are located at the same distance behind the mirror as the object in front of it is mainly used in interior decoration and in architecture to make rooms appear brighter and bigger. Moreover, placing a mirror near lights, chandeliers and table lamps reflects the light over a larger area, and makes the room appear brighter. Images that cannot be captured on a screen are called virtual images.

Left–Right Inversion

As the name suggests, images are laterally inverted, i.e. the right part of an object appears on the left in its image, and the left part of the object appears on the right. For example, the word AMBULANCE is painted left-right inverted on the ambulance so that when the driver of a vehicle in front looks into his rear-view mirror, he can make out the word AMBULANCE quickly and give way.

Characteristics of Image Formed in a Plane Mirror

The image formed by a plane mirror is:
     •  of the same size as that of the object
     •  left-right inverted
     •  erect and virtual
     •  as far behind the mirror as the object is in front of it.

A mirror maze is created based on the principle of reflection in plane mirrors. The maze has several plane mirrors placed at fixed angles to each other. When a person enters a mirror maze, he finds several images of himself and several passages. There is only one passage that is real, while all the others are just images.

Videos

Activities




Activity 1

pearson.com.au has created an interative simulation in which one can change the position of the light source or the angle of the mirror to see how the angle of reflection changes. This simulation gives a virtual experimental set up to verify the law of reflection for different angles of incidence. One can see that the law is valid for all colours of light. Also there is a fun game to test the understanding of reflection of light.

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Activity 2

sciencekids has deveoped an interactive online activity in which one can choose and drag a plane mirror in the path of light to illuminate various objects. By changing the position of the mirror the angle of incidence and hence the angle of reflection can be changed. Two mirrors can be used simultaneously too.

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References

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