Question

What is the angle of deviation produced by a glass slab ? Explain with a ray diagram.

Answer 1

Hint: In order to solve this problem first draw a ray diagram and label it. And also see how refraction through a glass slab occurs.
Now check, if incident ray and emergent ray are parallel to each other, then the angle of deviation is 0.
If incident ray and emergent ray are not parallel to each other, then the angle of deviation is not 0.

Complete step by step answer:
Angle of deviation is the angle between the direction of the refracted ray and the direction of the incident ray when a ray of light passes from one medium to another.
We can easily understand the refraction through a glass slab with the help of a ray diagram.

According to diagram we can see when a light incidents on the one surface of glass slab then the light deviates towards normal because when light travels rarer to denser medium then its moves towards normal.And when it emerges out from the other face it deviates away from the normal because now light travels from denser medium to rarer medium.
Hence, the incident ray and emergent ray are parallel to each other. So, the angle of deviation is 0.

Note:
Many times students may get confused between deviation by a glass prism and a glass slab. The difference is :
By a Glass slab : It deviates from the actual path but the direction of the incident ray and emergent ray of light are parallel to each other.
By a Glass prism : It deviates from the actual path but the direction of the incident ray and emergent ray of light are not parallel to each other.