Visible Light

Question 1

What is visible light?

Answer 1

The only part of the EM spectrum we can see with the naked eye

Question 2

What is specular reflection? (3)

Answer 2

1. When light hits a smooth, shiny surface (e.g. a mirror), all rays will reflect in a single direction.
2. The angle of incidence will always equal the angle of reflection
3. Produces an image

Question 3

What is diffuse reflection? (2)

Answer 3

1. When light hits a rough surface, all rays will scatter in many directions
2. Does not produce an image.

Question 4

What is white light?

Answer 4

White light is a mixture of all colours that each have a different narrow band of wavelength and frequency

Question 5

How is light dispersed in a prism?

Answer 5

1. When white light enters a prism, it is refracted - each colour is refracted by a different amount
2. Red light has the longest wavelength and refracts the least while violet light has the shortest wavelength and refracts the most, creating a spectrum of colours as the light leaves the prism.

Question 6

Describe opaque, translucent and transparent objects in terms of light.

Answer 6

1. Opaque - transmits no light, so we can’t see through them
2. Translucent - scatters light rays so we can’t see through them clearly
3. Transparent - all light is transmitted, so we can see clearly through

Question 7

What determines the colour of an object?

Answer 7

The wavelengths of visible light that are reflected and absorbed

Question 8

Why do white, black and red objects appear those colours?

Answer 8

1. White - they reflect all wavelengths of visible light equally
2. Black - absorb all wavelengths equally
3. Red - absorb all wavelengths expect red which is reflected

Question 9

How do we see colour?

Answer 9

When light is reflected off of an object, it is absorbed by the light receptors in our eyes and transmits messages to the brain which then produce sensations of colour.

Question 10

What three colours can humans see?

Answer 10

Red, blue and green (primary colours of light)

Question 11

How do we see?

Answer 11

1. Our retinas have light-sensitive cells called rods and cones that send info to the brain as impulses via the optic nerve allowing us to see.
2. Rods process black and white info and are concentrated around the edges of the retinas
3. Cones distinguish colours and are found in the middle of the retina

Question 12

What are the three varieties of cones?

Answer 12

Sensitive to long (red and orange), medium (yellow and green), or short (blue and purple) wavelengths.