ICSE Class 10: Refraction of Light Videos | Refractive index and speed of light

• I cannot understand how to find angles and find the path of the ray of light passing through a prism, pls help me 
• why does vibgyor have same speed in vaccum
• What is refractive index?
• why does the speed of light vary in diffrent medium ? class 10 icse physics 
• why does the speed increase or decrease in a medium i.e what are the factors that affect the speed of light in a medium and how?  
• multiple image formation in refraction lesson
• Can the angle of refraction in denser medium be more than the critical angle for the pair of media when the light ray is travelling from rarer to denser medium?
• (a) Choose the correct statement with respect to Refraction of light [1] 1. The colour always changes when light enters from one optical medium to another. 2. Absorption of light when it strikes the surface of a medium is refraction. 3. Speed of light changes when it enters from one optical medium to another of different optical density. 4. Speed of light does not change when it enters from one optical medium to another of different optical density.
• what is refraction
• what is an mirage

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