The EM Spectrum And Light Rays

Question 1

What are the uses of radio waves

Answer 1

Radio broadcast

Question 2

What are 2 uses for microwaves

Answer 2

Communication + cooking

Question 3

What is the speed of EM waves

Answer 3

3x10^8 m/s (the speed of light)

Question 4

What is infrared used for

Answer 4

Night vision, remote controls

Question 5

What is visible light used for

Answer 5

Seeing, photography

Question 6

What is UV light used for

Answer 6

Detecting counterfeit documents and currency

Question 7

What are x-rays used for

Answer 7

Observation of the bones of the human body

Question 8

What are gamma rays used for

Answer 8

Sterilising food and medical equipment

Question 9

What are some sources of radiowaves

Answer 9

Radio transmitters, tv transmitters

Question 10

What are some sources of microwaves

Answer 10

Microwaves and ovens

Question 11

What is the source of IR

Answer 11

Hot objects

Question 12

What is the source of visible light

Answer 12

Luminous objects

Question 13

What is the source of UV

Answer 13

The sun and UV lamps

Question 14

What are the sources of x-rays

Answer 14

X-ray tubes

Question 15

What is the source of gamma rays

Answer 15

Radioactive materials

Question 16

Which has the highest frequency

Answer 16

Gamma rays

Question 17

Which wave type on the EM spectrum has the largest wavelength

Answer 17

Radiowaves

Question 18

What are the dangers of microwaves

Answer 18

They heat water molecules because they absorb the microwaves - meaning they could also heat human body tissue

Question 19

Do all object emit IR

Answer 19

Yes

Question 20

What are some of the dangers of IR

Answer 20

Skin burns

Question 21

What are the dangers of radio waves

Answer 21

Heats human body tissue

Question 22

What are the dangers of visible light

Answer 22

Retina damage

Question 23

What are the dangers of ultraviolet light

Answer 23

Causes skin to age prematurely and skin cancer

Question 24

What are the dangers of x-rays

Answer 24

Cell damage and cancer

Question 25

What are the dangers of gamma rays

Answer 25

Damaging DNA and cancer

Question 26

What is reflection

Answer 26

When a ray of light strikes a plane (flat) mirror, it is reflected so that the angle of incidence (i) is equal to the angle of reflection (r)

Question 27

What is a normal line

Answer 27

A perpendicular line drawn at the point where the ray meets the mirror

Question 28

What is refraction

Answer 28

When light passes through a medium like air, water, glass etc, the ray is slowed down, therefore refracted towards the normal, assuming it is going into an object with a greater refractive index e.g. from air into glass

Question 29

Where is the normal line for refraction

Answer 29

Perpendicular to the boarder between mediums

Question 30

When does refraction happen

Answer 30

When a light ray passes from one medium to another

Question 31

When is there no refraction (2)

Answer 31

When the light ray hits the medium at a perpendicular angle to the boarder When it is all reflected (TIR)

Question 32

What equation is used to calculate the refractive index

Answer 32

n = sin i/sin r

Question 33

What is i

Answer 33

The angle of incidence

Question 34

What is r

Answer 34

The angle of reflection/refraction

Question 35

What is total internal reflection

Answer 35

When all of the light ray is reflected back into the medium off the boarder, rather than passing through the medium

Question 36

What is the critical angle in refraction

Answer 36

The angle of incidence when the refracted ray runs along the boarder

Question 37

Where are the two light rays produced when a light ray passes through a medium

Answer 37

1. The refracted ray that passes over the boundary 2. A weak ray is reflected, with the same angle of the angle of incidence

Question 38

How do ships find out how far they are from the bottom of the surface

Answer 38

1. Send a sound wave down to the sea floor 2. Measure how long it takes for you to receive it again 3. You already know the speed of the wave Use speed = distance/time to find distance (be careful that you divide time by two because it has to go down and up to be received)

Question 39

What equation links critical angle and refractive index

Answer 39

Sin critical angle = 1/refractive index

Question 40

What letter represents refractive index

Answer 40

n

Question 41

What happens to a ray of light when it refracts towards the normal

Answer 41

It slows down

Question 42

What happens to a ray of light when it refracts away from the normal

Answer 42

It speeds up

Question 43

Where are angles drawn from on a refraction/reflection diagram

Answer 43

Between the ray and the **normal** (not the border

Question 44

How to draw the normal line

Answer 44

Perpendicular to the tangent at the point at which the light ray enters a new medium (for non straight borders) Perpendicular to the point of intersection with the border (straight line border)