CBSE Class 7 Physics Notes- Chapter 5 Light

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                      CHAPTER 5 LIGHT
 
Light always travels in a straight line.
 
REFLECTION
When a beam of light hits a surface, its direction changes. This is called reflection of light.
 
IMAGE FORMED BY A MIRROR
When we look into a mirror, we see our reflection which is nothing but our image which is formed behind the mirror.
An image is formed at the same distance behind the mirror as the distance of the object from the mirror.
An image is laterally inverted i.e. the right of the object is left in the image and the left of the object is right in the image.
Mirrors can also be curved. Such mirrors are called spherical mirrors. If the reflecting surface is concave, it is called a concave mirror and if the reflecting surface is convex, it is called a convex mirror.
 
IMAGE FORMED BY A LENS
A convex lens is a lens which is thicker in the middle and thinner at the edges while a concave lens is a lens which is thinner in the middle and thicker at the edges.
A convex lens generally converges light and a concave lens generally diverges light. Lenses are used in magnifying glasses, spectacles, telescopes, etc.
A convex lens forms a real, inverted image of the object. However, if the object is placed too close to the lens, it forms a virtual, erect and magnified image.
A concave lens forms an erect, virtual and smaller image of the object
 
WHITE LIGHT
Sunlight appears to be white but it is not. White light is composed of seven different colours. These colours mix together to look like white. The seven colours are: Violet, Indigo, Blue, Green, Yellow, Orange, Red.

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