Friday, 21 October 2011

Class 7 - Science Chapter 15 - Light

 Class 7 - Science Chapter 15 - Light

1. Light travels along straight lines. This property is called rectilinear propagation of light.

2. Any polished or a shining surface acts as a mirror.

3. Change in direction of light from an object is called reflection of light.

4. An image which can be obtained on a screen is called a real image.

5. An image which cannot be obtained on a screen is called a virtual image.

6. The image formed by a plane mirror is erect. It is virtual and is of the same size as the object. The image is at the same distance behind the mirror as the object is in front of it.

7. In an image formed by a mirror, the left side of the object is seen on the right side in the image, and right side of the object appears to be on the left side in the image. This property is called Lateral Inversion.



8. A concave mirror can form a real and inverted image. When the object is placed very close to the mirror, the image formed is virtual, erect and magnified.

9. Image formed by a convex mirror is erect, virtual and smaller in size than the object.

10. A convex lens can form real and inverted image. When the object is placed very close to the lens, the image formed is virtual, erect and magnified. When used to see objects magnified, the convex lens is called a magnifying glass.

11. A concave lens always forms erect, virtual and smaller image than the object.

12. White light is composed of seven colours. i.e. VIBGYOR (alsp called spectrum of light)
V - violet
I - indigo
B - blue
G - green
Y - yellow
O - orange
R- red


13. A rainbow consists of all the seven colours of white light.

14. A prism splits white light into its seven constituent colours.

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