GCSE Physics - Refraction of waves #63

Summary

This video explains the concept of light wave refraction, which occurs when waves change direction as they move between different mediums, like air and glass. It covers how wave speed varies with material density, ray diagrams, and triangular prisms. The video demonstrates how light bends towards or away from the normal when passing into more or less dense mediums, and how wavelength changes while frequency remains constant. Additionally, it explains how different colors in white light refract differently, spreading out like a rainbow when passed through a prism.

Takeaways

• 💡 Refraction is the process where light waves change direction as they pass from one medium to another.
• 🌊 Waves travel at different speeds in different materials due to variations in density.
• 🔍 Electromagnetic waves, like light, slow down when moving through a denser medium.
• ↘️ When a wave moves from a less dense medium (e.g., air) to a more dense medium (e.g., glass), it bends towards the normal line.
• 📏 Ray diagrams are used to illustrate the refraction of light as it travels through different mediums.
• 🖊️ To draw a ray diagram, first establish the normal line at the point of incidence where the light hits the surface.
• ➡️ As the wave enters a denser medium, it bends towards the normal, slowing down.
• ↗️ Upon exiting a dense medium back to a less dense medium, the wave bends away from the normal and speeds up.
• 📐 The angles of incidence and refraction are used to define the direction change in ray diagrams.
• 🌈 White light passing through a triangular prism spreads into a spectrum of colors because different wavelengths refract by different amounts.

Q & A

What is refraction?

Refraction is the bending or change in direction of light waves as they pass from one medium to another with a different density, such as from air into glass.

Why do light waves refract when they enter a different medium?

Light waves refract because they travel at different speeds in different media. This change in speed, due to the varying densities of the materials, causes the light waves to bend at the boundary.

How does the density of a medium affect the speed of light waves?

In denser media, light waves travel more slowly. The higher the density, the slower the light wave moves through the medium.

What happens to a light wave that hits the boundary between two media at an angle?

When a light wave hits the boundary at an angle, it changes direction and bends either towards or away from the normal line depending on the densities of the media.

How does the direction of bending change when light enters a denser medium?

When light enters a denser medium, it bends towards the normal, which is an imaginary line perpendicular to the surface at the point of incidence.

What is a ray diagram, and why is it used in the study of refraction?

A ray diagram is a graphical representation that shows the path of light as it moves through different media. It helps to visualize how light waves bend and change direction during refraction.

What is the refracted ray, and how is it drawn in a ray diagram?

The refracted ray is the light ray that has changed direction after entering a new medium. In a ray diagram, it is drawn from the point of incidence, bending towards the normal if entering a denser medium.

What is the emergent ray in a refraction diagram?

The emergent ray is the light ray that exits the second medium. If the ray moves from a denser to a less dense medium, it bends away from the normal as it emerges.

How does the wavelength of light change when it refracts, and why?

The wavelength of light changes during refraction because the wave speed changes. According to the wave speed equation, as the speed of the wave decreases, the wavelength also decreases, and vice versa.

Why do different wavelengths of light refract by different amounts in a triangular prism?

Different wavelengths of light refract by varying amounts because each wavelength experiences a different change in speed. This separation causes a white light beam to spread out into its component colors, creating a spectrum or rainbow effect.