2 - Refraction Explain what happens when light moves through a transparent medium of different density 3 - Reflection

**2- Refraction:**<br /><br />When light moves from one transparent medium to another with a different density, its speed changes. This change in speed causes the light to bend, a phenomenon known as refraction. The degree of bending depends on the angle at which the light strikes the interface between the two media and the refractive indices of the two media. The refractive index of a medium is a measure of how much light slows down in that medium compared to its speed in a vacuum.<br /><br />Here's a breakdown:<br /><br />* **From less dense to more dense:** When light moves from a less dense medium (like air) to a more dense medium (like water or glass), it slows down. This causes the light to bend *towards* the normal (an imaginary line perpendicular to the surface at the point of incidence).<br />* **From more dense to less dense:** When light moves from a more dense medium (like water or glass) to a less dense medium (like air), it speeds up. This causes the light to bend *away* from the normal.<br /><br />Think of a car driving from pavement onto sand at an angle. The wheel that hits the sand first slows down, causing the car to turn slightly towards the perpendicular to the edge of the pavement.<br /><br />Refraction is responsible for many optical phenomena we observe, such as the apparent bending of a straw in a glass of water or the formation of rainbows.<br /><br />**3- Reflection:**<br /><br />Reflection is the bouncing back of light when it strikes a surface. The angle at which the light strikes the surface (angle of incidence) is equal to the angle at which it reflects (angle of reflection). Both angles are measured relative to the normal (the imaginary line perpendicular to the surface at the point of incidence). This is known as the law of reflection.<br /><br />There are two main types of reflection:<br /><br />* **Specular reflection:** This occurs when light reflects off a smooth surface, like a mirror. The reflected rays are parallel, resulting in a clear image.<br />* **Diffuse reflection:** This occurs when light reflects off a rough surface. The reflected rays scatter in different directions, resulting in a blurry or no image. Most objects we see are visible due to diffuse reflection. The light from a source, like the sun or a lamp, hits the object and is scattered in all directions. Some of this scattered light reaches our eyes, allowing us to see the object.<br />