Topic 5 - Light And Electromagnetic Spectrum

Question 1

What is total internal reflection?

Answer 1

When light is completely reflected back at a boundary between 2 mediums

Question 2

When does total internal reflection happen?

Answer 2

When light meets less dense medium at angle of incidence larger than critical angle

Question 3

What is the critical angle?

Answer 3

Angle of incidence which causes angle of reflection to be 90°

Question 4

What determines the colour of visible light waves?

Answer 4

Wavelength and frequency of light waves

Question 5

What colour of visible light has the highest frequency?

Answer 5

Blue

Question 6

What colour of visible light has the largest wavelength?

Answer 6

Red

Question 7

What is meant by the term ‘specular reflection’

Answer 7

Rays are reflected from a smooth surface in a single direction

Question 8

What is meant by the term ‘diffuse reflection’

Answer 8

Reflection from a rough surface which causes scattering

Question 9

How does a red colour filter work?

Answer 9

It absorbs all wavelengths of light other than those in the red range of the spectrum
(Only red light passes through it)

Question 10

What is meant by the term ‘opaque’

Answer 10

Not see through

Question 11

What governs the colour of an opaque object?

Answer 11

Different objects reflect different wavelengths of light by different amounts.
Wavelengths most strongly reflected determine the colour.

Question 12

What happens to the wavelengths of light that aren’t reflected by an opaque object?

Answer 12

Absorbed by object

Question 13

What colour does an object appear if all wavelengths are reflected by equal amounts?

Answer 13

White

Question 14

What colour does an object appear if all wavelengths are absorbed?

Answer 14

Black

Question 15

What type of waves are electromagnetic waves?

Answer 15

Transverse

Question 16

What do electromagnetic waves transfer?

Answer 16

Energy

Question 17

What type of spectrum do electromagnetic waves form?

Answer 17

Continuous spectrum

Question 18

Lost the order of the magnetic spectrum (decreasing wavelength)

Answer 18

Radio, Microwaves, Infrared, Visible, UV, X Ray, Gamma

Question 19

What is the highest frequency electromagnetic wave?

Answer 19

Gamma waves

Question 20

What is the highest energy electromagnetic wave?

Answer 20

Gamma waves

Question 21

What properties are shared by all electromagnetic waves?

Answer 21

All transverse
All travel at 3x10^8 m/s
Can travel through vacuum

Question 22

What is a convex lens?

Answer 22

Thicker in middle than top

Question 23

What do light rays do in a convex lens?

Answer 23

Converge towards focal point/principal focus

Question 24

Distance from lens to principal focus = ?

Answer 24

Focal length

Question 25

What is a concave lens?

Answer 25

Thinner in middle than top

Question 26

What do light rays do in a concave lens?

Answer 26

Diverge

Question 27

What can an image formed by a lens be?

Answer 27

- upright or inverted - magnified or diminished - real or virtual

Question 28

What does a shorter focal length mean?

Answer 28

More powerful lens

Question 29

What is the power of the lens defined as?

Answer 29

Reciprocal of the focal length

Question 30

Equation for power of a lens

Answer 30

P (D) = 1/focal length

Question 31

What type of focal lengths and power values do the lenses have?

Answer 31

``` Convex = positive Concave = negative ```

Question 32

When is an image real?

Answer 32

When the rays intersect

Question 33

When is an image virtual?

Answer 33

When the rays meet if they were produced backwards

Question 34

What is the image when an object is placed more than 2x the focal length from lens? (Convex)

Answer 34

Inverted Diminished Real

Question 35

What is the image when an object is placed between 1 and 2 focal lengths from the lens? (Convex)

Answer 35

Inverted Magnified Real

Question 36

What is the image when the object is placed at a distance less than the focal length (convex)?

Answer 36

Upright Magnified Virtual

Question 37

What toe of waves can be produced by oscillations in an electrical circuit?

Answer 37

Radio waves

Question 38

How can radio waves create an alternating current in a circuit?

Answer 38

When absorbed, they can induce oscillations in a circuit with the same frequency as the waves themselves

Question 39

Where do gamma rays originate from?

Answer 39

Originate from changes in the nuclei of atoms

Question 40

What health effects can ultraviolet waves cause?

Answer 40

Skin to age prematurely | Increased risk of developing skin cancer

Question 41

What health effects can X rays and gamma rays cause?

Answer 41

Ionising radiation can cause mutations in genes | Can lead to increased risk of developing various cancers

Question 42

What health effects can infrared rays cause?

Answer 42

Infrared waves can cause burns to skin/tissue

Question 43

How does electromagnetic radiation affect electron arrangement in atoms?

Answer 43

Absorption or emission of electromagnetic radiation can cause electron arrangement to change.

Question 44

What are the effects of body cells absorbing radiation?

Answer 44

Large amounts can damage cells | Smaller amounts cause mutations causing cells to divide rapidly - lead to cancer

Question 45

State and explain use of radio waves

Answer 45

Communications - long wavelength so can travel far

Question 46

State and explain a use of microwaves

Answer 46

Cooking - microwaves are absorbed by and heat fat/water in foods

Question 47

State and explain uses of infrared radiation

Answer 47

Cooking food Infrared cameras Short range communication

Question 48

State and explain uses of visible light

Answer 48

Illuminating + fibre optics (reflect best in glass)

Question 49

State and explain uses of UV radiation

Answer 49

Sterilisation - kills bacteria Energy efficient lamps - radiates low heat but high energy Sun tanning

Question 50

State and explain uses of X rays

Answer 50

Medical imaging + treatment | High energy and can easily penetrate body tissues

Question 51

State and explain uses of gamma rays

Answer 51

Medical treatments - radiotherapy

Question 52

Which waves of EM spectrum are regarded as most dangerous?

Answer 52

Gamma and X rays - highest energy