Lesson 1

Question 1

The Nature of Light

Answer 1

Sun gives off large amounts of energy, (solar radiation)

energy travels through space as electromagnetic waves

Question 2

Electromagnetic wave

Answer 2

energy in the form of a wave
associated with electric and magnetic fields
can travel though vacuums at the speed of light or a medium
all waves are invisible except visible light
each wave is assigned a wave length and a frequency.

Question 3

Wavelength

Answer 3

the distance between peaks on a wave

Question 4

Frequency

Answer 4

the number of complete wavelengths that pass a given point in 1 second

Question 5

electromagnetic spectrum

Answer 5

the arrangement of all electromagnetic waves according to their wave length and frequency
low energy ->longer wavelength -> low frequency
high energy ->shorter wavelength ->higher frequency
each electromagnetic wave has a different amount of energy and wavelength
They all travel at the same speed

Question 6

seven types of electromagnetic waves

Answer 6

Radio waves,
microwaves,
infrared  light,
visible light
ultraviolet light, x rays
and gamma rays

Question 7

Visible light

Answer 7

any electromagnetic wave hat the human eye can see

can be separated into many colours: red, orange, yellow, green, blue, indigo and violet

Question 8

visible spectrum

Answer 8

the continuous sequence of colours that together form visible white light
different colours of light in the visible spectrum have different amounts of energy.
red light has the least amount of energy
violet light has the most energy

Question 9

Sources of light

Answer 9

Light comes from natural source
human made sources
luminous object
gives off its own light
produces light by changing other forms of energy to light
non luminous object
does not give off its own light
may appear bright because their surfaces reflect light from a luminous object
for all light sources, stops must absorb some form of energy and in excited state. then immediately the excited atoms release the energy often in the form of light

Question 10

Incandescence

Answer 10

substances produce light when heated to a very high temperature

Question 11

Incandescence light bulb

Answer 11

electrical energy ->heat+light
is very inefficient 
->95% given off as heat
->5% is changed to light
electrical current runs through a tiny filament
->filament gets very hot
->filament glows

Question 12

fuel-burning technologies

Answer 12

chemical energy-> heat +light
olympic torch
butane lamps

Question 13

light from luminescence

Answer 13

substances produce light when they have not been heated

Question 14

electric discharge

Answer 14

when electricity passes through a gas, the gas can give off light
electric current passes through a gas/vapour
->gas heats up
->gas gives off light
street lights
neon lighting

Question 15

fluorescence

Answer 15

objects produce light when the substance (phosphor) absorb ultraviolet radiation and immediately change it to visible light
very efficient
->last longer
->use less electrical energy for same brightness

Question 16

phosphorescence

Answer 16

light is produced when the substances (phosphorescent )absorb invisible UV radiation and change it to visible light over a longer period of time
glow in the dark t-shirts coated with phosphorescent materials.

Question 17

chemiluminescence

Answer 17

light is produced from a chemical reaction between two chemicals
chemical energy ->light energy
glow sticks

Question 18

bioluminescence

Answer 18

light is produced from a chemical reaction in living organisms
occurs in living things to scare predator, lure preys, or attract mates
fireflies, glow worms, certain bacteria, fish

Question 19

The light emitting diode (LED)

Answer 19

LED diode allows electric current to flow in only one direction using semiconductors (silicon)
->save energy
->last longer
->stay cooler than both incandescent bulbs and compact fluorescent light bulbs of similar bulbs.
christmas lights, traffic lights.