1.12 Visible Light & Colour

Question 1

What does the colour of an object depend on?

Answer 1

The differences in its absorption, transmission and reflection of different wavelengths

Question 2

What are the only 3 colours you cant make by mixing?

Answer 2

• Pure red
• Green
• Blue

Question 3

What are opaque objects?

Answer 3

Objects that do not transmit light

Question 4

What happens when visible light waves hit opaque objects?

Answer 4

They absorb some wavelengths of light and reflect others

Question 5

The colour of the object depends on which wavelengths of light are __________.

Answer 5

Reflected, e.g. a red apple appears to be red because the wavelengths corresponding to the red part of the visible spectrum are reflected. The other wavelengths of light are absorbed

Question 6

Describe how opaque objects that aren’t primary colours display their colour

Answer 6

For opaque objects that aren’t a primary colour, they may be reflecting either the wavelengths of light corresponding to that colour, or the wavelengths of the primary colours that can mix together to make that colour

Question 7

What wavelengths of light do white objects reflect?

Answer 7

white objects reflect (or scatter) all of the wavelengths of visible light equally

Question 8

What wavelengths of light do black objects absorb/transmit/reflect?

Answer 8

Black objects absorb all wavelengths of visible light (and scatter none). Your eyes see black as the lack of any visible light (i.e. the lack of any colour)

Question 9

Do transparent and translucent objects absorb/reflect/transmit light?

Answer 9

Transparent (see-through) and translucent (partially see-through) objects transmit light, i.e. not all light that hits the surface of the object is absorbed or reflected - some can pass through (most can for transparent objects). Some wavelengths of light may be absorbed/reflected by translucent objects (and to a lesser extent by transparent objects). These objects will appear to be the colour of light that corresponds to the wavelengths most strongly transmitted by the object

Question 10

Does red have a long/short wavelength or a low/high frequency?

Answer 10

Long wavelength, low frequency

Question 11

Does violet have a long/short wavelength or low/high frequency?

Answer 11

Short wavelength, high frequency

Question 12

Why do objects appear the colour they do? (2)

Answer 12

• Wavelengths of light hitting it
• Properties of that object
  Together, these will determine which light rays are absorbed, reflected or transmitted and so determine how the object appears

Question 13

How much of the light do translucent objects transmit and how does this determine how well we can see through them?

Answer 13

Only transmit some of the light - the proportion of light they transmit determines how well we can see through them. The colour of translucent objects is determined by which wavelengths are transmitted the most

Question 14

What do colour filters do?

Answer 14

They’re used to filter out different wavelengths of light, so that only certain wavelengths are transmitted. They work by only transmitting certain wavelengths of light while absorbing the rest

Question 15

What is a primary colour filter?

Answer 15

A filter that only allows one of the three primary colours to be transmitted, e.g. if white light is shone at a blue colour filter, only blue light will be let through. The rest of the light will be absorbed

Question 16

If you looked at a blue object through a green filter, how would it appear?

Answer 16

It would appear black because the filter would block the blue light from passing through and so no light would be reflected into your eye

Question 17

What wavelengths of light do filters that aren’t for primary colours let through?

Answer 17

They let through both the wavelengths of light for that colour AND the wavelengths of the primary colours that add together to make that colour

Question 18

What wavelengths of light does a yellow filter let through?

Answer 18

It lets through yellow wavelengths of light and red and green as it adds to make yellow

Question 19

What wavelengths of light does an indigo colour filter let through?

Answer 19

It lets through indigo, and red and blue as they combine to make indigo

Question 20

Why does a green glass bottle appear green?

Answer 20

The bottle reflects and/or transmits green light and absorbs other colours of light