CBSE Class 10 Answered

glass is an surface object and prism is an dimensional object which has interier angles...hence when light passes through a prism it gets dispersed.if a prism and an invertedly placed prism kept together , we get only white light In a glass slab, the edges where the refraction of light takes place are PARALLEL to each other, thus all the seven colours of the light are refracted by the same amount and by the same angle at both the surfaces. But in a glass prism, the two surfaces where refraction takes place are NOT PARALLEL to each other...so all the colours of the light are refracted by different amounts and by different angles...the violet colour being refracted the most and red colour being refracted the least(due to having different frequencies).