A light ray in air enters and passes through a block of glass. What can be stated with regard to its speed after it emerges from the block? Speed is less than when in glass. Speed is less than before it entered glass. Speed is same as that in glass. Speed is same as that before it entered glass.

Speed is same as that before it entered glass.

Explanation:

Given:

A light ray enters and passes through the glass as shown in the diagram.

We have to analyze its speed.

Speed of light in air is and speed of light in glass is

Whenever a light ray enters a glass block or slab there is bending of light at the interface of the two media.

So speed of light will decrease in glass medium and again it passes to the air.

So

Speed of light in air will again increase or will be equivalent to the earlier speed when it was entering the glass block.

Finally

Speed is same as that before it entered glass as it in the same medium (air).

total distance/total time

(85 + 82)/(5+3)

167/8

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