1. Change in Speed:
Light travels at different speeds in different mediums. It travels fastest in a vacuum (like space), slower in air, and even slower in water or glass. When light enters a denser medium (one where it travels slower), it slows down.
2. Bending of Light:
Because of the change in speed, light changes direction. This bending of light is called refraction. The amount of bending depends on:
* The angle of incidence: The angle at which the light hits the surface.
* The indices of refraction of the two mediums: Each material has a unique refractive index, which describes how much it bends light.
3. Reflection:
Some of the light may also be reflected back into the original medium at the boundary between the two. This is why you can see your reflection in a window or a mirror.
Consequences of Refraction:
* Magnifying Glass: A magnifying glass uses the refraction of light through a curved lens to make objects appear larger.
* Prisms: Prisms use refraction to separate white light into its component colors, creating a rainbow effect.
* Fish in Water: Fish appear closer to the surface than they actually are due to the refraction of light as it passes from water to air.
* Seeing through Glass: We can see through glass because light is refracted at the surfaces, but the bending is relatively small.
Understanding the Physics:
* Snell's Law: This law mathematically describes the relationship between the angles of incidence and refraction, and the refractive indices of the two mediums.
* Wave Nature of Light: Refraction can be explained by considering light as a wave. When light passes from one medium to another, the wavelength changes, leading to a change in direction.
In short, light bends when it travels from one medium to another because its speed changes, and this bending is essential for many optical phenomena we see in everyday life.
