P14.3 Light and colour

Question 1

What do stars and lamps such as filament lamps emit?

Answer 1

Light that has a continuous range of wavelengths across the visible spectrum

Question 2

How to colour filters work?

Answer 2

They work by absorbing certain wavelengths and transmitting other wavelengths

Question 3

What does the colour of a surface depend on?

Answer 3

Depends on chemicals called pigments in the surface material

Question 4

Why does a white surface look white?

Answer 4

It has no pigments so it reflect light of any wavelength - either partially or totally
Surface looks white in the daylight because daylight is white light and the reflected light includes all the colors of white light

Question 5

How can you investigate the reflection of a narrow beam of light from a ray box by using different surfaces?

Answer 5

In a darkened room - place the ray box on a blank sheet paper so that you can see you the light on the paper
Use the ray box to direct a light ray as a plane mirror. Repeat at different angles of incidence
Then replace the mirror with different coloured surfaces

Compare reflection of a narrow beam of light from a shiny surface with the same narrow beam reflected from a surface

Question 6

What are transparent object?

Answer 6

Transmit all the incident light that enters the object
No light is absorbed at the surface
Transmitted light travels through the object

Question 7

What are Translucent objects?

Answer 7

Objects let light pass through them - but the light is scattered or refracted
This happens because the material of the object has internal boundaries that change the direction of the light rays repeatedly.

Question 8

What is an opaque object?

Answer 8

It is an object that absorbs all the light that reaches it

The light is either reflected or scattered at the surface