This video explains about the convex Lens . A convex lens is the lens that is thick at centre and thin at the edges. It has two surfaces and hence it has two principal foci or two focal points. A convex lens is called converging lens.
This video explains about the concave lens . One surface of the curved mirror is silvered. If the reflection takes place at the concave surface ( which is towards the centre of the sphere it is called a concave mirror.
This video explains nature of light. It also explains that Sunlight is considered as white light and through an experiment it is proved it consists of seven different colour. It also explains about Newton's disc.
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