Flag Wave Optics> my teacher said that during refraction by...
question mark

my teacher said that during refraction by a glass slab, the light bends because in glass its speed is reduced and so as to take the normal time, it tends to cover shorter distance and thus bends by certain angle...... but in case of a prism, it goes towards the base of the prism however in this case its path is the longer one......please help me to solve this problem.....

Shane Macguire , 11 Years ago
Grade upto college level
anser 1 Answers
Askiitians Tutor Team

Last Activity: 14 Days ago

It sounds like you're grappling with some interesting concepts in optics! Let's break down the differences between refraction through a glass slab and a prism, focusing on how light behaves in each scenario.

Refraction in a Glass Slab

When light passes from air into a glass slab, it slows down due to the higher density of glass compared to air. This change in speed causes the light to bend towards the normal line, which is an imaginary line perpendicular to the surface at the point of incidence. The bending occurs because light takes the path that minimizes the time taken to travel from one point to another, a principle known as Fermat's principle of least time.

Why Does Light Bend?

  • Speed Change: In air, light travels faster than in glass. When it enters glass, its speed decreases, causing it to bend.
  • Normal Line: The normal line helps us visualize the angle at which light enters and exits the medium.
  • Path Length: Although the distance traveled in glass is shorter, the light still takes less time to travel through the medium due to its reduced speed.

Refraction in a Prism

Now, when light enters a prism, the situation changes. A prism has angled surfaces, which means that as light enters, it bends towards the base of the prism. This bending occurs twice: once when entering the prism and again when exiting it.

Understanding the Path of Light in a Prism

  • Entry and Exit Angles: The light bends towards the normal when it enters the prism and bends away from the normal when it exits, leading to a net bending towards the base.
  • Longer Path: While it may seem counterintuitive that light takes a longer path, the angles involved and the change in speed still result in a quicker overall travel time through the prism compared to a straight path.
  • Dispersion: Additionally, different wavelengths of light bend at different angles, leading to the separation of colors, which is a fascinating effect of prisms.

Putting It All Together

In summary, while both a glass slab and a prism cause light to bend due to changes in speed, the geometry of the prism introduces additional angles that affect the light's path. In a slab, the bending is straightforward and uniform, while in a prism, the angles create a more complex path that ultimately leads to bending towards the base. Understanding these principles helps clarify why light behaves differently in various mediums and shapes.

Feel free to ask more questions if you need further clarification on any of these points!

star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments