Question

when a thick glass slab is placed over some printed matter, the letters appear raised when viewed through glass slab. Why?

A lemon kept in water in a glass tumbler appears to be bigger than its actual size, when viewed from sides.Why?

Answer 1

The letters appear raised because of a phenomenon known as refraction. When light travels from one medium to another, it bends (either towards or away from the normal). This happens because different media have different densities and thus, the speed of light is different in each one of them. This causes the light to slow down or speed up, depending on the medium. Note that refraction takes place at the interface of two media, air and glass in this case. Also note that refraction only takes place when the light is incident obliquely to the medium and not along a normal drawn to it.

Answer 2

When we keep the glass slab over some printed matter, the light coming from the letters (after reflection ) face change of medium at glass-air interface. Since glass has more refractive index than air, the light bends away from the normal as it goes out of glass. This apparently causes us to see the letters raised. This phenomenon is called as refraction of light.

Hope this clarified your doubt.
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