refraction, reflection + colours

What is reflection?

When waves bounce off a surface that cannot transmit them.

What are the two types of reflection?

Specular and diffuse reflection.

Define specular reflection.

Reflection off smooth surfaces in a single beam, making the same angle with the normal as the incident beam.

Define diffuse reflection.

Reflection off a rough surface, resulting in scattering of light.

What kind of image is produced by reflection off a plane mirror?

A virtual image.

What is a virtual image?

An image produced on the same side of the lens as the object; cannot be formed on a screen because rays never cross.

What measurements should be taken when investigating reflection?

The angle of incidence and the angle of reflection.

What is the angle of incidence?

The angle (relative to the normal) at which light hits the mirror.

What is the angle of reflection?

The angle (relative to the normal) at which light leaves the mirror.

What is the normal?

A line perpendicular to the surface of the mirror.

What apparatus is needed to investigate reflection?

Ray box, plane mirror, pencil, paper, protractor.

Describe a method to investigate reflection.

Shine rays at various angles onto a plane mirror, trace the rays, measure angles of incidence and reflection using a protractor.

What should you observe from the results?

Angle of incidence = angle of reflection.

What is refraction?

A change in speed of a wave at a boundary between two media, usually causing a change in direction.

What apparatus is needed to investigate refraction?

Ray box, prism, paper, pencil, protractor.

Describe a method to investigate refraction.

Trace the prism, shine light through it, trace incident and refracted rays, draw normals, measure angles.

What is white light made of?

All the colours of the visible spectrum.

What happens when white light passes through a prism?

It is dispersed into a spectrum of colours.

Why does a prism split white light into colours?

Different colours refract by different amounts because they have different wavelengths.

Which colour refracts the most in a prism?

Violet.

Which colour refracts the least in a prism?

Red.

Why do different colours refract by different amounts?

Each colour has a different wavelength, so they change speed by different amounts in the prism.

What determines the colour of an opaque object?

The colour it reflects.

What determines the colour of a transparent object?

The colour it transmits.

Why does a red object appear red?

It reflects red light and absorbs other colours.

Why does a blue filter make objects look blue?

It transmits blue light and absorbs other colours.

What happens when an object reflects no light?

It appears black.