Visible Light + Colours + Filters

What is white light?

Light containing all the colours of the visible spectrum.

What happens when white light passes through a prism?

It undergoes dispersion, separating into different colours.

Why does a prism separate white light into colours?

Different wavelengths are refracted by different amounts.

What is dispersion?

The separation of light into its component colours.

Which colour of visible light has the highest frequency?

Violet.

Which colour of visible light has the lowest frequency?

Red.

Why do objects appear coloured?

They reflect or transmit certain wavelengths of visible light and absorb others.

Why does a red object appear red in white light?

It reflects red wavelengths more strongly and absorbs many other visible wavelengths.

Why does a white object appear white?

It reflects all visible wavelengths approximately equally.

Why does a black object appear black?

It absorbs most visible wavelengths and reflects very little visible light.

What is an opaque object?

An object that does not transmit light.

What is a transparent material?

A material that transmits light with little scattering, allowing objects to be seen clearly.

What is a translucent material?

A material that transmits but scatters light, preventing a clear image.

What is a colour filter?

A material that transmits certain wavelengths of light and absorbs others.

How does a red filter affect white light?

It transmits red light and absorbs most other visible colours.

What happens when white light passes through a blue filter?

Mainly blue light is transmitted.

Why can a red object appear black under blue light?

It absorbs most blue light and has little red light available to reflect.

Why does a coloured filter make some objects appear darker?

It absorbs wavelengths that those objects would otherwise reflect.

Can a red filter turn blue light into red light?

No, it mainly absorbs the blue light rather than changing its colour.

What happens when light is reflected from a smooth surface?

Specular reflection occurs, producing reflected rays in a regular direction.

What happens when light is reflected from a rough surface?

Diffuse reflection occurs, scattering light in different directions.

Why can we see ordinary non-luminous objects?

Light from a source is reflected by the objects into our eyes.

Why does an opaque blue object look blue in white light?

It reflects blue wavelengths more strongly and absorbs many other visible wavelengths.

Why can the same object appear different colours under different lighting?

The wavelengths available to be reflected depend on the incident light.