Question

a pencil when dipped in water in a glass tumbler appears to be bent at the intersurface

Answer 1

Due to refraction, when the light goes from air (rarer medium) to water (denser medium) then the light rays moves away from the normal. That's why when pencil dipped in water (denser medium) from air (rarer medium) then the pencil looks like it is bent but in real it doesn't bent.

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