Picturing the scene: Imagine yourself at the beach on a sunny day. You decide to take a dive and, as you're underwater, you notice a peculiar effect - the sunlight seems to bend and sometimes even bounce back! Let's dig into why this happens.

• What's Happening: When waves move from one medium to another (like from water to air), they change speed and direction. This is called refraction.
• Easy Peasy Lemon Squeezy Example: Think of driving a car from a tar road onto sand. The car slows down and might even change direction if you enter at an angle.

• Wave speed in the first medium v₁​ > Wave speed in the second medium v₂​.
• Result: The angle of the wave changes. In a ripple tank, waves refract towards the normal in shallower water.

• We're imagining a setup where light moves from water to air.
  • Ray A: Straight-up ray! Moves straight and a tiny bit reflects back.
  • Ray B: Slightly tilted ray. A little of it reflects back into the water.
  • Ray C: More tilted! It's deviating quite a bit from its original direction.
  • Ray D: The diva ray. It just grazes the water's edge. Here's where the "critical angle" (θc​) comes into play.
  • Ray E: No light enters the air. Only strong reflection in the water. This is the show-stealer, folks! It's called "Total Internal Reflection."

🎉 Fun Fact: This total internal reflection is what makes diamonds sparkle!